From Wikipedia, the free encyclopedia


A rotary dial telephone, c.1940s


Modern telephones use push buttons

A telephone, or phone, is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be heard directly. A telephone converts sound, typically and most efficiently the human voice, into electronic signals that are transmitted via cables and other communication channels to another telephone which reproduces the sound to the receiving user.

In 1876, Scottish emigrant Alexander Graham Bell was the first to be granted a United States patent for a device that produced clearly intelligible replication of the human voice. This instrument was further developed by many others. The telephone was the first device in history that enabled people to talk directly with each other across large distances. Telephones rapidly became indispensable to businesses, government, and households, and are today some of the most widely used small appliances.

The essential elements of a telephone are a microphone (transmitter) to speak into and an earphone (receiver) which reproduces the voice in a distant location. In addition, most telephones contain a ringer which produces a sound to announce an incoming telephone call, and a dial or keypad used to enter a telephone number when initiating a call to another telephone. Until approximately the 1970s most telephones used a rotary dial, which was superseded by the modern DTMF push-button dial, first introduced to the public by AT&T in 1963. The receiver and transmitter are usually built into a handset which is held up to the ear and mouth during conversation. The dial may be located either on the handset, or on a base unit to which the handset is connected. The transmitter converts the sound waves to electrical signals which are sent through a telephone network to the receiving telephone which converts the signals into audible sound in the receiver, or sometimes a loudspeaker. Telephones are duplex devices, meaning they permit transmission in both directions simultaneously.

The first telephones were directly connected to each other from one customer’s office or residence to another customer’s location. Being impractical beyond just a few customers, these systems were quickly replaced by manually operated centrally located switchboards. This gave rise to landline telephone service in which each telephone is connected by a pair of dedicated wires to a local central office switching system, which developed into fully automated systems starting in the early 1900s. For greater mobility, various radio systems were developed for transmission between mobile stations on ships and automobiles in the middle 20th century. Hand-held mobile phones were introduced for personal service starting in 1973. By the late 1970s several mobile telephone networks operated around the world. In 1983, the Advanced Mobile Phone System (AMPS) was launched, offering a standardized technology providing portability for users far beyond the personal residence or office. These analog cellular system evolved into digital networks with better security, greater capacity, better regional coverage, and lower cost. Today, the worldwide public switched telephone network, with its hierarchical system of many switching centers, can connect any telephone on the network with any other. With the standardized international numbering system, E.164, each telephone line has an identifying telephone number, that may be called from any other, authorized telephone on the network.

Although originally designed for simple voice communications, convergence has enabled most modern cell phones to have many additional capabilities. They may be able to record spoken messages, send and receive text messages, take and display photographs or video, play music or games, surf the Internet, do road navigation or immerse the user in virtual reality. Since 1999, the trend for mobile phones is smartphones that integrate all mobile communication and computing needs.

Basic Principles


Schematic of a landline telephone installation.

A traditional landline telephone system, also known as plain old telephone service (POTS), commonly carries both control and audio signals on the same twisted pair (C in diagram) of insulated wires, the telephone line. The control and signaling equipment consists of three components, the ringer, the hookswitch, and a dial. The ringer, or beeper, light or other device (A7), alerts the user to incoming calls. The hookswitch signals to the central office that the user has picked up the handset to either answer a call or initiate a call. A dial, if present, is used by the subscriber to transmit a telephone number to the central office when initiating a call. Until the 1960s dials used almost exclusively the rotary technology, which was replaced by dual-tone multi-frequency signaling (DTMF) with pushbutton telephones (A4).

A major expense of wire-line telephone service is the outside wire plant. Telephones transmit both the incoming and outgoing speech signals on a single pair of wires. A twisted pair line rejects electromagnetic interference (EMI) and crosstalk better than a single wire or an untwisted pair. The strong outgoing speech signal from the microphone (transmitter) does not overpower the weaker incoming speaker (receiver) signal with sidetone because a hybrid coil (A3) and other components compensate the imbalance. The junction box (B) arrests lightning (B2) and adjusts the line’s resistance (B1) to maximize the signal power for the line length. Telephones have similar adjustments for inside line lengths (A8). The line voltages are negative compared to earth, to reduce galvanic corrosion. Negative voltage attracts positive metal ions toward the wires.

Details of Operation

The landline telephone contains a switchhook (A4) and an alerting device, usually a ringer (A7), that remains connected to the phone line whenever the phone is “on hook” (i.e. the switch (A4) is open), and other components which are connected when the phone is “off hook”. The off-hook components include a transmitter (microphone, A2), a receiver (speaker, A1), and other circuits for dialing, filtering (A3), and amplification.

A calling party wishing to speak to another party will pick up the telephone’s handset, thereby operating a lever which closes the switchhook (A4), which powers the telephone by connecting the transmitter (microphone), receiver (speaker), and related audio components to the line. The off-hook circuitry has a low resistance (less than 300 ohms) which causes a direct current (DC), which comes down the line (C) from the telephone exchange. The exchange detects this current, attaches a digit receiver circuit to the line, and sends a dial tone to indicate readiness. On a modern push-button telephone, the caller then presses the number keys to send the telephone number of the called party. The keys control a tone generator circuit (not shown) that makes DTMF tones that the exchange receives. A rotary-dial telephone uses pulse dialing, sending electrical pulses, that the exchange can count to get the telephone number (as of 2010 many exchanges were still equipped to handle pulse dialing). If the called party’s line is available, the exchange sends an intermittent ringing signal (about 75 volts alternating current (AC) in North America and UK and 60 volts in Germany) to alert the called party to an incoming call. If the called party’s line is in use, the exchange returns a busy signal to the calling party. However, if the called party’s line is in use but has call waiting installed, the exchange sends an intermittent audible tone to the called party to indicate an incoming call.

The ringer of a telephone (A7) is connected to the line through a capacitor (A6), which blocks direct current but passes the alternating current of the ringing signal. The telephone draws no current when it is on hook, while a DC voltage is continually applied to the line. Exchange circuitry (D2) can send an AC current down the line to activate the ringer and announce an incoming call. When there is no automatic exchange, telephones have hand-cranked magnetos to generate a ringing voltage back to the exchange or any other telephone on the same line. When a landline telephone is inactive (on hook), the circuitry at the telephone exchange detects the absence of direct current to indicate that the line is not in use. When a party initiates a call to this line, the exchange sends the ringing signal. When the called party picks up the handset, they actuate a double-circuit switchhook (not shown) which may simultaneously disconnects the alerting device and connects the audio circuitry to the line. This, in turn, draws direct current through the line, confirming that the called phone is now active. The exchange circuitry turns off the ring signal, and both telephones are now active and connected through the exchange. The parties may now converse as long as both phones remain off hook. When a party hangs up, placing the handset back on the cradle or hook, direct current ceases in that line, signaling the exchange to disconnect the call.

Calls to parties beyond the local exchange are carried over trunk lines which establish connections between exchanges. In modern telephone networks, fiber-optic cable and digital technology are often employed in such connections. Satellite technology may be used for communication over very long distances.

In most landline telephones, the transmitter and receiver (microphone and speaker) are located in the handset, although in a speakerphone these components may be located in the base or in a separate enclosure. Powered by the line, the microphone (A2) produces a modulated electric current which varies its frequency and amplitude in response to the sound waves arriving at its diaphragm. The resulting current is transmitted along the telephone line to the local exchange then on to the other phone (via the local exchange or via a larger network), where it passes through the coil of the receiver (A3). The varying current in the coil produces a corresponding movement of the receiver’s diaphragm, reproducing the original sound waves present at the transmitter.

Along with the microphone and speaker, additional circuitry is incorporated to prevent the incoming speaker signal and the outgoing microphone signal from interfering with each other. This is accomplished through a hybrid coil (A3). The incoming audio signal passes through a resistor (A8) and the primary winding of the coil (A3) which passes it to the speaker (A1). Since the current path A8 – A3 has a far lower impedance than the microphone (A2), virtually all of the incoming signal passes through it and bypasses the microphone.

At the same time the DC voltage across the line causes a DC current which is split between the resistor-coil (A8-A3) branch and the microphone-coil (A2-A3) branch. The DC current through the resistor-coil branch has no effect on the incoming audio signal. But the DC current passing through the microphone is turned into AC current (in response to voice sounds) which then passes through only the upper branch of the coil’s (A3) primary winding, which has far fewer turns than the lower primary winding. This causes a small portion of the microphone output to be fed back to the speaker, while the rest of the AC current goes out through the phone line.

A lineman’s handset is a telephone designed for testing the telephone network, and may be attached directly to aerial lines and other infrastructure components.


Alexander_Graham_Telephone_in_Newyork (1)

Bell placing the first New York to Chicago telephone call in 1892

Before the development of the electric telephone, the term “telephone” was applied to other inventions, and not all early researchers of the electrical device called it “telephone”. A communication device for sailing vessels The Telephone was the invention of a captain John Taylor in 1844. This instrument used four air horns to communicate with vessels in foggy weather. Later, c. 1860, Johann Philipp Reis used the term in reference to his Reis telephone, his device appears to be the first such device based on conversion of sound into electrical impulses, the term telephone was adopted into the vocabulary of many languages. It is derived from the Greek: τῆλε, tēle, “far” and φωνή, phōnē, “voice”, together meaning “distant voice”.

Credit for the invention of the electric telephone is frequently disputed. As with other influential inventions such as radio, television, the light bulb, and the computer, several inventors pioneered experimental work on voice transmission over a wire and improved on each other’s ideas. New controversies over the issue still arise from time to time. Charles Bourseul, Antonio Meucci, Johann Philipp Reis, Alexander Graham Bell, and Elisha Gray, amongst others, have all been credited with the invention of the telephone.

Alexander Graham Bell was the first to be awarded a patent for the electric telephone by the United States Patent and Trademark Office (USPTO) in March 1876. The Bell patents were forensically victorious and commercially decisive. That first patent by Bell was the master patent of the telephone, from which other patents for electric telephone devices and features flowed.

In 1876, shortly after the telephone was invented, Hungarian engineer Tivadar Puskás invented the telephone switch, which allowed for the formation of telephone exchanges, and eventually networks.

Early Development


Reis’ telephone


Acoustic telephone ad, The Consolidated Telephone Co., Jersey City, NJ 1886


1896 telephone from Sweden


Wooden wall telephone with a hand-cranked magneto generator

  • 1844: Innocenzo Manzetti first mooted the idea of a “speaking telegraph” or telephone. Use of the “speaking telegraph” and “sound telegraph” monikers would eventually be replaced by the newer, distinct name, “telephone”.
  • 26 August 1854: Charles Bourseul published an article in the magazine L’Illustration (Paris): “Transmission électrique de la parole” (electric transmission of speech), describing a “make-and-break” type telephone transmitter later created by Johann Reis.
  • 26 October 1861: Johann Philipp Reis (1834–1874) publicly demonstrated the Reis telephone before the Physical Society of Frankfurt. Reis’ telephone was not limited to musical sounds. Reis also used his telephone to transmit the phrase “Das Pferd frisst keinen Gurkensalat” (“The horse does not eat cucumber salad”).
  • 22 August 1865, La Feuille d’Aoste reported “It is rumored that English technicians to whom Mr. Manzetti illustrated his method for transmitting spoken words on the telegraph wire intend to apply said invention in England on several private telegraph lines”. However telephones would not be demonstrated there until 1876, with a set of telephones from Bell.
  • 28 December 1871: Antonio Meucci files patent caveat No. 3335 in the U.S. Patent Office titled “Sound Telegraph”, describing communication of voice between two people by wire. A ‘patent caveat’ was not an invention patent award, but only an unverified notice filed by an individual that he or she intends to file a regular patent application in the future.
  • 1874: Meucci, after having renewed the caveat for two years does not renew it again, and the caveat lapses.
  • 6 April 1875: Bell’s U.S. Patent 161,739 “Transmitters and Receivers for Electric Telegraphs” is granted. This uses multiple vibrating steel reeds in make-break circuits.
  • 11 February 1876: Gray invents a liquid transmitter for use with a telephone but does not build one.
  • 14 February 1876: Elisha Gray files a patent caveat for transmitting the human voice through a telegraphic circuit.
  • 14 February 1876: Alexander Graham Bell applies for the patent “Improvements in Telegraphy”, for electromagnetic telephones using what is now called amplitude modulation (oscillating current and voltage) but which he referred to as “undulating current”.
  • 19 February 1876: Gray is notified by the U.S. Patent Office of an interference between his caveat and Bell’s patent application. Gray decides to abandon his caveat.
  • 7 March 1876: Bell’s U.S. patent 174,465 “Improvement in Telegraphy” is granted, covering “the method of, and apparatus for, transmitting vocal or other sounds telegraphically…by causing electrical undulations, similar in form to the vibrations of the air accompanying the said vocal or other sound.”
  • 10 March 1876: The first successful telephone transmission of clear speech using a liquid transmitter when Bell spoke into his device, “Mr. Watson, come here, I want to see you.” and Watson heard each word distinctly.
  • 30 January 1877: Bell’s U.S. patent 186,787 is granted for an electromagnetic telephone using permanent magnets, iron diaphragms, and a call bell.
  • 27 April 1877: Edison files for a patent on a carbon (graphite) transmitter. The patent 474,230 was granted 3 May 1892, after a 15-year delay because of litigation. Edison was granted patent 222,390 for a carbon granules transmitter in 1879.

Early commercial Instruments

Early telephones were technically diverse. Some used a water microphone, some had a metal diaphragm that induced current in an electromagnet wound around a permanent magnet, and some were dynamic – their diaphragm vibrated a coil of wire in the field of a permanent magnet or the coil vibrated the diaphragm. The sound-powered dynamic variants survived in small numbers through the 20th century in military and maritime applications, where its ability to create its own electrical power was crucial. Most, however, used the Edison/Berliner carbon transmitter, which was much louder than the other kinds, even though it required an induction coil which was an impedance matching transformer to make it compatible with the impedance of the line. The Edison patents kept the Bell monopoly viable into the 20th century, by which time the network was more important than the instrument.

Early telephones were locally powered, using either a dynamic transmitter or by the powering of a transmitter with a local battery. One of the jobs of outside plant personnel was to visit each telephone periodically to inspect the battery. During the 20th century, telephones powered from the telephone exchange over the same wires that carried the voice signals became common.

Early telephones used a single wire for the subscriber’s line, with ground return used to complete the circuit (as used in telegraphs). The earliest dynamic telephones also had only one port opening for sound, with the user alternately listening and speaking (or rather, shouting) into the same hole. Sometimes the instruments were operated in pairs at each end, making conversation more convenient but also more expensive.

At first, the benefits of a telephone exchange were not exploited. Instead telephones were leased in pairs to a subscriber, who had to arrange for a telegraph contractor to construct a line between them, for example between a home and a shop. Users who wanted the ability to speak to several different locations would need to obtain and set up three or four pairs of telephones. Western Union, already using telegraph exchanges, quickly extended the principle to its telephones in New York City and San Francisco, and Bell was not slow in appreciating the potential.

Signalling began in an appropriately primitive manner. The user alerted the other end, or the exchange operator, by whistling into the transmitter. Exchange operation soon resulted in telephones being equipped with a bell in a ringer box, first operated over a second wire, and later over the same wire, but with a condenser (capacitor) in series with the bell coil to allow the AC ringer signal through while still blocking DC (keeping the phone “on hook”). Telephones connected to the earliest Strowger switch automatic exchanges had seven wires, one for the knife switch, one for each telegraph key, one for the bell, one for the push-button and two for speaking. Large wall telephones in the early 20th century usually incorporated the bell, and separate bell boxes for desk phones dwindled away in the middle of the century.

Rural and other telephones that were not on a common battery exchange had a magneto hand-cranked generator to produce a high voltage alternating signal to ring the bells of other telephones on the line and to alert the operator. Some local farming communities that were not connected to the main networks set up barbed wire telephone lines that exploited the existing system of field fences to transmit the signal.

In the 1890s a new smaller style of telephone was introduced, packaged in three parts. The transmitter stood on a stand, known as a “candlestick” for its shape. When not in use, the receiver hung on a hook with a switch in it, known as a “switchhook”. Previous telephones required the user to operate a separate switch to connect either the voice or the bell. With the new kind, the user was less likely to leave the phone “off the hook”. In phones connected to magneto exchanges, the bell, induction coil, battery and magneto were in a separate bell box or “ringer box”. In phones connected to common battery exchanges, the ringer box was installed under a desk, or other out of the way place, since it did not need a battery or magneto.

Cradle designs were also used at this time, having a handle with the receiver and transmitter attached, now called a handset, separate from the cradle base that housed the magneto crank and other parts. They were larger than the “candlestick” and more popular.

Disadvantages of single wire operation such as crosstalk and hum from nearby AC power wires had already led to the use of twisted pairs and, for long distance telephones, four-wire circuits. Users at the beginning of the 20th century did not place long distance calls from their own telephones but made an appointment to use a special soundproofed long distance telephone booth furnished with the latest technology.

What turned out to be the most popular and longest lasting physical style of telephone was introduced in the early 20th century, including Bell’s 202-type desk set. A carbon granule transmitter and electromagnetic receiver were united in a single molded plastic handle, which when not in use sat in a cradle in the base unit. The circuit diagram of the model 202 shows the direct connection of the transmitter to the line, while the receiver was induction coupled. In local battery configurations, when the local loop was too long to provide sufficient current from the exchange, the transmitter was powered by a local battery and inductively coupled, while the receiver was included in the local loop. The coupling transformer and the ringer were mounted in a separate enclosure, called the subscriber set. The dial switch in the base interrupted the line current by repeatedly but very briefly disconnecting the line 1 to 10 times for each digit, and the hook switch (in the center of the circuit diagram) disconnected the line and the transmitter battery while the handset was on the cradle.

In the 1930s, telephone sets were developed that combined the bell and induction coil with the desk set, obviating a separate ringer box. The rotary dial becoming commonplace in the 1930s in many areas enabled customer-dialed service, but some magneto systems remained even into the 1960s. After World-War II, the telephone networks saw rapid expansion and more efficient telephone sets, such as the model 500 telephone in the United States, were developed that permitted larger local networks centered around central offices. A breakthrough new technology was the introduction of Touch-Tone signaling using push-button telephones by American Telephone & Telegraph Company (AT&T) in 1963.


Ericsson DBH 1001 (ca. 1931), the first combined telephone made with a Bakelite housing and handset.


Telephone used by American soldiers (WWII, Minalin, Pampanga, Philippines)


Video shows the operation of an Ericofon


AT&T push button telephone made by Western Electric model 2500 DMG black 1980


A candlestick phone


Modern sound-powered emergency telephone


A mobile phone, also called a cell phone

Digital telephones and voice over IP


An IP desktop telephone attached to a computer network, with touch-tone dialing


Fixed telephone lines per 100 inhabitants 1997–2007

The invention of the transistor in 1947 dramatically changed the technology used in telephone systems and in the long-distance transmission networks. With the development of electronic switching systems in the 1960s, telephony gradually evolved towards digital telephony which improved the capacity, quality, and cost of the network.

The development of digital data communications method, such as the protocols used for the Internet, it became possible to digitize voice and transmit it as real-time data across computer networks, giving rise to the field of Internet Protocol (IP) telephony, also known as voice over Internet Protocol (VoIP), a term that reflects the methodology memorably. VoIP has proven to be a disruptive technology that is rapidly replacing traditional telephone network infrastructure.

As of January 2005, up to 10% of telephone subscribers in Japan and South Korea have switched to this digital telephone service. A January 2005 Newsweek article suggested that Internet telephony may be “the next big thing.” As of 2006 many VoIP companies offer service to consumers and businesses.

From a customer perspective, IP telephony uses a high-bandwidth Internet connection and specialized customer premises equipment to transmit telephone calls via the Internet, or any modern private data network. The customer equipment may be an analog telephone adapter (ATA) which interfaces a conventional analog telephone to the IP networking equipment, or it may be an IP Phone that has the networking and interface technology built into the desk-top set and provides the traditional, familiar parts of a telephone, the handset, the dial or keypad, and a ringer in a package that usually resembles a standard telephone set.

In addition, many computer software vendors and telephony operators provide softphone application software that emulates a telephone by use of an attached microphone and audio headset, or loud speaker.

Despite the new features and conveniences of IP telephones, some may have notable disadvantages compared to traditional telephones. Unless the IP telephone’s components are backed up with an uninterruptible power supply or other emergency power source, the phone ceases to function during a power outage as can occur during an emergency or disaster when the phone is most needed. Traditional phones connected to the older PSTN network do not experience that problem since they are powered by the telephone company’s battery supply, which will continue to function even if there is a prolonged power outage. Another problem in Internet-based services is the lack of a fixed physical location, impacting the provisioning of emergency services such as police, fire or ambulance, should someone call for them. Unless the registered user updates the IP phone’s physical address location after moving to a new residence, emergency services can be, and have been, dispatched to the wrong location.


Graphic symbols used to designate telephone service or phone-related information in print, signage, and other media include ℡ (U+2121), ☎ (U+260E), ☏ (U+260F), ✆ (U+2706), and ⌕ (U+2315).


In 2002, only 10% of the world’s population used cell phones and by 2005 that percentage had risen to 46%.  By the end of 2009, there were a total of nearly 6 billion mobile and fixed-line telephone subscribers worldwide. This included 1.26 billion fixed-line subscribers and 4.6 billion mobile subscribers.


  • “US 174,465”.—Telegraphy (Bell’s first telephone patent)—Alexander Graham Bell
  • US 186,787—Electric Telegraphy (permanent magnet receiver)—Alexander Graham Bell
  • US 474,230—Speaking Telegraph (graphite transmitter)—Thomas Edison
  • US 203,016—Speaking Telephone (carbon button transmitter)—Thomas Edison
  • US 222,390—Carbon Telephone (carbon granules transmitter)—Thomas Edison
  • US 485,311—Telephone (solid back carbon transmitter)—Anthony C. White (Bell engineer) This design was used until 1925 and installed phones were used until the 1940s.
  • US 3,449,750—Duplex Radio Communication and Signalling Appartus—G. H. Sweigert
  • US 3,663,762—Cellular Mobile Communication System—Amos Edward Joel (Bell Labs)
  • US 3,906,166—Radio Telephone System (DynaTAC cell phone)—Martin Cooper et al. (Motorola)

Urinary Catheterization

From Wikipedia, the free encyclopedia

Opera 800px-Urinary_catheterization_with_a_doll

In urinary catheterization a latex, polyurethane, or silicone tube known as a urinary catheter is inserted into a patient’s bladder via the urethra. Catheterization allows the patient’s urine to drain freely from the bladder for collection. It may be used to inject liquids used for treatment or diagnosis of bladder conditions. A clinician, often a nurse, usually performs the procedure, but self-catheterization is also possible. The catheter may be a permanent one (indwelling catheter), or an intermittent catheter removed after each catheterization.

Catheter Types

Catheters come in several basic designs:

  • A Foley catheter (indwelling urinary catheter) is retained by means of a balloon at the tip that is inflated with sterile water. The balloons typically come in two different sizes: 5 cm3 and 30 cm3. They are commonly made in silicone rubber or natural rubber.
  • An intermittent catheter/Robinson catheter is a flexible catheter used for short term drainage of urine. Unlike the Foley catheter, it has no balloon on its tip and therefore cannot stay in place unaided. These can be non-coated or coated (e.g., hydrophilic coated and ready to use).
  • Intermittent self catheterization in males is best performed with a flexible catheter to drain the bladder periodically. The procedure should not be attempted by a patient without guidance in maintaining cleanliness of the catheter and surrounding area and specific instruction regarding catheter insertion from meatus to bladder entry.
  • A coudé catheter, including Tiemann’s catheter, is designed with a curved tip that makes it easier to pass through the curvature of the prostatic urethra.
  • A hematuria (or haematuria) catheter is a type of Foley catheter used for Post-TURP hemostasis. This is useful following endoscopic surgical procedures, or in the case of gross hematuria. There are both two-way and three-way hematuria catheters (double and triple lumen).
  • An condom catheter is used for incontinent males and carries a lower risk of infection than an indwelling catheter.
  • Catheter diameters are sized by the French catheter scale (F). The most common sizes are 10 F (3.3mm) to 28 F (9.3mm). The clinician selects a size large enough to allow free flow of urine, and large enough to control leakage of urine around the catheter. A larger size is necessary when the urine is thick, bloody, or contains large amounts of sediment. Larger catheters, however, are more likely to damage the urethra. Some people develop allergies or sensitivities to latex after long-term latex catheter use making it necessary to use silicone or Teflon types.

Evidence does not support an important decrease in the risk of urinary tract infections when silver-alloy catheters are used.

Sex Differences

In males, the catheter tube is inserted into the urinary tract through the penis. A condom-type catheter (also known as a ‘Texas catheter’), if used, fits around the tip of the penis, rather than being inserted. In females, the catheter is inserted into the urethral meatus, after a cleansing using povidone-iodine. The procedure can be complicated in females due to varying layouts of the genitalia (due to age, obesity, female genital cutting, childbirth, or other factors), but a good clinician would rely on anatomical landmarks and patience when dealing with such a patient. In the UK it is generally accepted that cleaning the area surrounding the urethral meatus with 0.9% sodium chloride solution is sufficient for both male and female patients as there is no reliable evidence to suggest that the use of antiseptic agents reduces the risk of urinary tract infection.

Males may have a slightly higher incidence of bladder spasms. If bladder spasms occur, or there is no urine in the drainage bag, the catheter may be blocked by blood, thick sediment, or a kink in the catheter or drainage tubing. Sometimes spasms are caused by the catheter irritating the bladder, prostate, or penis. Such spasms can be controlled with medication such as butylscopolamine, although most patients eventually adjust to the irritation and the spasms go away.

Common indications to catheterize a patient include acute or chronic urinary retention (which can damage the kidneys), orthopedic procedures that may limit a patient’s movement, the need for accurate monitoring of input and output (such as in an ICU), benign prostatic hyperplasia, incontinence, and the effects of various surgical interventions involving the bladder and prostate.

For some patients the insertion and removal of a catheter causes excruciating pain, so a topical anesthetic is used. Catheterization would be performed as a sterile medical procedure by trained, qualified personnel, using equipment designed for this purpose, except in the case of intermittent self-catheterization where patients have been trained to perform the procedure themselves.

Intermittent self-catheterization is performed by the patient four to six times a day, using a clean technique in most cases. Nurses use a sterile technique to perform intermittent catheterization in hospital settings. Incorrect technique may cause trauma to the urethra or prostate (male), urinary tract infection, or a paraphimosis in the uncircumcised male. For patients with spinal cord lesions and neurogenic bladder dysfunction, intermittent catheterisation (IC) is a standard method for bladder emptying. The technique is safe and effective and results in improved kidney and upper urinary tract status, lessening of vesicoureteral reflux and amelioration of continence. In addition to the clinical benefits, patient quality of life is enhanced by the increased independence and security offered by self-catheterization.



Foley catheter


Condom catheter


Male Self-Catheterization


Female Self-Catheterization


Male foley catheter

Catheter Maintenance

A catheter that is left in place for more than a short period of time is generally attached to a drainage bag to collect the urine. This also allows for measurement of urine volume. There are three types of drainage bags: The first is a leg bag, a smaller drainage device that attaches by elastic bands to the leg. A leg bag is usually worn during the day, as it fits discreetly under pants or skirts, and is easily emptied into a toilet. The second type of drainage bag is a larger device called a down drain that may be used overnight. This device is hung on a hook under the patient’s bed—never placed on the floor, due to risk of bacterial infection. The third is called a belly bag, and is secured around the waist. This bag can be worn at all times. It can be worn under the patient’s underwear to provide a totally undetectable look.

During long-term use, the catheter may be left in place all the time, or a patient may be instructed on a procedure for placing a catheter just long enough to empty the bladder and then removing it (known as intermittent self-catheterization). Patients undergoing major surgery are often catheterized and may remain so for some time. The patient may require irrigation of the bladder with sterile saline injected through the catheter to flush out clots or other matter that does not drain.



How to properly drain a condom catheter.


How to properly drain a Foley catheter.


Illustration of a closed urinary drainage method.


Illustration of how to empty a urinary drainage bag.

Effects of long term use

The duration of catheterization can have significance. Incontinent patients commonly are catheterized to reduce their cost of care. However, long-term catheterization carries a significant risk of urinary tract infection.   Because of this risk catheterization is a last resort for the management of incontinence where other measures have proved unsuccessful. Other long term complications may include blood infections (sepsis), urethral injury, skin breakdown, bladder stones, and blood in the urine (hematuria). After many years of catheter use, bladder cancer may also develop.

Preventing infection

Everyday care of catheter and drainage bag is important to reduce the risk of infection. Such precautions include:

  • Cleansing the urethral area (area where catheter exits body) and the catheter itself.
  • Disconnecting drainage bag from catheter only with clean hands
  • Disconnecting drainage bag as seldom as possible.
  • Keeping drainage bag connector as clean as possible and cleansing the drainage bag periodically.
  • Use of a thin catheter where possible to reduce risk of harming the urethra during insertion.
  • Drinking sufficient liquid to produce at least two liters of urine daily
  • Sexual activity is very high risk for urinary infections, especially for catheterized women.
  • There is no clear evidence that any one catheter type or insertion technique is superior than another in preventing infection.

Recent developments in the field of the temporary prostatic stent have been viewed as a possible alternative to indwelling catheterization and the infections associated with their use.


From Wikipedia, the free encyclopedia


Bifocals are eyeglasses with two distinct optical powers. Bifocals are commonly prescribed to people with presbyopia who also require a correction for myopia, hyperopia, and/or astigmatism.


Bifocals with separate lenses


Benjamin Franklin is generally credited with the invention of bifocals. Historians have produced some evidence to suggest that others may have come before him in the invention; however, a correspondence between George Whatley and John Fenno, editor of The Gazette of the United States, suggested that Franklin had indeed invented bifocals, and perhaps 50 years earlier than had been originally thought. Since many inventions are developed independently by more than one person, it is possible that the invention of bifocals may have been such a case. Nonetheless, Benjamin Franklin was among the first to wear bifocal lenses, and Franklin’s letters of correspondence suggest that he invented them independently, regardless of whether he was the first to invent them.

John Isaac Hawkins, the inventor of trifocal lenses, coined the term bifocals in 1824 and credited Dr. Franklin.

In 1955, Irving Rips of Younger Optics created the first seamless or “invisible” bifocal, a precursor to all progressive lenses.


Original bifocals were designed with the most convex lenses (for close viewing) in the lower half of the frame and the least convex lenses on the upper. Up until the beginning of the 20th century two separate lenses were cut in half and combined together in the rim of the frame. The mounting of two half lenses into a single frame led to a number of early complications and rendered such spectacles quite fragile. A method for fusing the sections of the lenses together was developed by Louis de Wecker at the end of the 19th century and patented by Dr. John L. Borsch, Jr. in 1908. Today most bifocals are created by molding a reading segment into a primary lens and are available with the reading segments in a variety of shapes and sizes.The most popular is the D-segment, 28 mm wide. While the D-segment bifocal offers superior optics, an increasing number of people opt for progressive bifocal lenses.


Bifocals can cause headaches and even dizziness in some users. Acclimation to the small field of view offered by the reading segment of bifocals can take some time, as the user learns to move either the head or the reading material rather than the eyes. Computer monitors are generally placed directly in front of users and can lead to muscle fatigue due to the unusual straight and constant movement of the head. This trouble is mitigated by the use of trifocal lenses or by the use of monofocal lenses for computer users.

In an interesting legal case reported in the UK in 1969, the plaintiff’s ability to use bifocals was impaired by accident.


Research continues in an attempt to eliminate the limited field of vision in current bifocals. New materials and technologies may provide a method which can selectively adjust the optical power of a lens. Researchers have constructed such a lens using a liquid crystal layer sandwiched between two glass substrates.

Bifocals in the animal world

The aquatic larval stage of the diving beetle Thermonectus marmoratus has, in its principal eyes, two retinas and two distinct focal planes that are substantially separated (in the manner of bifocals) to switch their vision from up-close to distance, for easy and efficient capture of their prey, mostly mosquito larvae. This is the first ever recorded use of bifocal technology in the animal world.

Franklin Stove

From Wikipedia, the free encyclopedia

The Franklin stove is a metal-lined fireplace named after Benjamin Franklin, who invented it in 1741. It had a hollow baffle near the rear (to transfer more heat from the fire to a room’s air) and relied on an “inverted siphon” to draw the fire’s hot fumes around the baffle. It was intended to produce more heat and less smoke than an ordinary open fireplace. It is also known as a “circulating stove” or the “Pennsylvania fireplace”.


A Franklin stove


The two distinguishing features of Franklin’s stove were a hollow baffle (i.e., a metal panel that directed the flow of the fire’s fumes) and a flue that acted as an upside-down siphon.


The Franklin stove. Cool air enters the baffle through a duct under the floor. Smoke exits through a U-shaped duct in the floor.

Baffles in fireplaces

Baffles were used to lengthen the path that either a room’s air or a fire’s fumes had to flow through ductwork, thereby allowing more heat to be transferred to the room’s air or from the fire’s fumes. Specifically, ducts could be installed within the brickwork around a hearth; cool room air would then enter the lower end of a duct, be heated by the hot walls of the duct, rise, and finally exit from the duct’s upper end and return to the room. The longer the path through which the air flowed, the more heat would be transferred from the fire to the air. Similarly, the longer the duct through which a fire’s fumes had to flow before reaching the chimney, more heat would be transferred from the fumes to the room’s air.

The use of baffles to extract more heat from a fire and its fumes was not new. In 1618, Franz Kessler (ca. 1580–1650) of Frankfurt-am-Main, Germany published Holzsparkunst (The Art of Saving Wood), featuring a stove in which the fumes from a fire were forced to snake through five chambers, one above the other, before entering the chimney. Kessler also documented an enclosed heating stove that, like Franklin’s stove, had a baffle directly behind the fire, thereby lengthening the path that the fire’s fumes had to travel before reaching the chimney.

In 1624, a French physician, Louis Savot (1579–1640), described a fireplace that he had built in the Louvre. Ducts passed under, behind, and above the fire in the hearth. Cool air in the room entered the lower opening of a duct, was warmed, rose, and returned to the room through the duct’s upper opening. In 1713, Frenchman Nicolas Gauger (ca. 1680–1730) published a book, La Mécanique du Feu… (The Mechanics of Fire), in which he presented novel designs for fireplaces. Gauger surrounded the hearth with hollow spaces. Inside these spaces were baffles. Cool room air entered the spaces through lower openings, was warmed as it snaked around the baffles in the spaces, and returned to the room through upper openings.

In Franklin’s stove, a hollow baffle was positioned inside and near the rear of the stove. The baffle was a wide but thin cast-iron box, which was open to the room’s air at its bottom and at two holes on its sides, near its top. Air entered the bottom of the box and was heated both by the fire and by the fumes flowing over the front and back of the box. The warmed air then rose inside the baffle and exited through the holes in the baffle’s sides. Franklin’s baffle thus performed at least two functions: like Kessler’s heating stove, it lengthened the path that the fire’s fumes had to follow before reaching the chimney, allowing more heat to be extracted from the fumes; and like Gauger’s fireplace, it placed a duct near the fire, which heated the room’s air via convection.

Inverted siphons in fireplaces

Some early experimenters reasoned that if a fire in a fireplace were connected by a U-shaped duct to the chimney, the hot gases ascending through the chimney would draw the fire’s smoke and fumes first downwards through one leg of the U and then upwards through the other leg and the chimney. This was what Franklin called an “aerial syphon” or “syphon revers’d”. This inverted siphon was used to draw the fire’s hot fumes up the front and down the back of the Franklin stove’s hollow baffle, in order to extract as much heat as possible from the fumes.

The earliest known example of such an inverted siphon was the 1618 fireplace of Franz Kessler. The fire burned in a ceramic box. Inside the box and behind the fire was a baffle. The baffle forced the fire’s fumes to descend behind the baffle before exiting to the chimney. The intention was to extract as much heat as possible from the fumes by extending the path that the fumes had to follow before they reached the chimney.

The 1678 fireplace of Prince Rupert (1619–1682) also included an inverted siphon. Rupert placed a hanging iron door between the fire grate and the chimney. In order to exit through the chimney, the fire’s fumes and smoke first had to descend below the edge of the door before rising through the chimney.

Another early example of an inverted siphon was a stove that was exhibited in 1686 at the annual Foire Saint-Germain, Paris. Its inventor, André Dalesme (1643–1727), called it a smokeless stove (furnus acapnos). The stove consisted of an iron bowl in which the fuel was burned. A pipe extended from the bowl’s bottom and then upwards into a chimney. Shortly after starting a fire in the bowl, hot air would begin to rise through the pipe and then up the chimney; this created a downward draft through the bowl, which drew the fire and its fumes down into the bowl. Once the draft was initiated, it was self-sustaining as long as the fire burned. Dalesme’s stove could burn wood, incense, and even “coal steept in cats-piss” yet produce very little smoke or smell. These results showed that fires could be used inside a room, without filling the house with smoke.

Franklin’s stove contained a baffle directly behind the fire, which forced the fire’s fumes to flow downward before they reached the chimney. This required a U-shaped duct in the floor behind the stove, so that the fumes could flow from the stove into the chimney. Thus Franklin’s stove incorporated an inverted siphon.

Franklin’s research and development

Gauger’s book on his innovative fireplace designs was translated into English – Fires Improv’d: Being a New Method of Building Chimneys, So as to Prevent their Smoaking (1715) – by a French immigrant to England, Jean Théophile Desaguliers (1683–1744). In a postscript to Desaguliers’ book A Course in Experimental Philosophy (1744), Desaguliers again briefly described Gauger’s fireplaces and mentioned his own work on the subject. Franklin read both of Desaguliers’ books and developed his own designs for a stove that could provide more heat with less smoke.

In 1742, Franklin finished his first design which implemented new scientific concepts about heat which had been developed by the Dutch physician Herman Boerhaave (1668–1738), a proponent of Isaac Newton’s ideas. Two years later, Franklin wrote a pamphlet describing his design and how it operated in order to sell his product. Around this time, the deputy governor of Pennsylvania, George Thomas, made an offer to Franklin to patent his design, but Franklin never patented any of his designs and inventions. He believed “that as we enjoy great advantages from the inventions of others, we should be glad of an opportunity to serve others by any invention of ours, and this we should do freely and generously”. As a result, many others were able to use Franklin’s design and improve it. Although his stove was intended to have the double purpose of cooking and heating a room, as time progressed and new stove designs became available, the Franklin stove’s main use became to heat a room. Many others improved on the Franklin stove design, but to this day, most American fireplaces are box-shaped, similar to the Franklin stove. The exception is the Rumford fireplace, developed by Benjamin Thompson.

Stove Design

The stove was about 30 inches (76 cm) tall, with a box shape. The front was open, except for a decorative panel in the upper part of the box. The back of the box was to be placed a few inches away from the flue (chimney). On the bottom panel there were several holes to allow the smoke to escape; these were connected to the chimney. The panels were bolted together with iron screws through pre-cast ears. Inside there was a small, thin rectangular prism that would force the smoke into the holes. The plates were all made from iron.

Franklin’s stove sold poorly. The problem lay with the inverted siphon: the smoke had to pass through a cold flue (which was set in the floor) before the smoke could enter the chimney; consequently, the smoke cooled too much and the stove did not have a good draft. The inverted siphon would operate properly only if the fire burned constantly, so that the temperature in the flue was high enough to produce a draft.

A later version, designed by David Rittenhouse, solved many of the problems Franklin’s original stove had and became popular. Franklin’s fame outweighed Rittenhouse’s, though, so history remembers the Franklin Stove rather than the Rittenhouse Stove.

Glass Harmonica

From Wikipedia, the free encyclopedia


Spinning glass disks (bowls) on a common shaft are arranged with the lower notes (larger disks) to the left and higher notes (smaller disks) to the right.

The glass harmonica, also known as the glass armonica, glass harmonium, bowl organ, hydrocrystalophone, or simply the armonica or harmonica (derived from ἁρμονία, harmonia, the Greek word for harmony), is a type of musical instrument that uses a series of glass bowls or goblets graduated in size to produce musical tones by means of friction (instruments of this type are known as friction idiophones).


A glass harp, an ancestor of the glass armonica, being played in Rome. The rims of wine glasses filled with water are rubbed by the player’s fingers to create the notes.

The name “glass harmonica” (also “glass armonica”, “glassharmonica”; harmonica de verre, harmonica de Franklin, armonica de verre, or just harmonica in French; Glasharmonika in German; harmonica in Dutch) refers today to any instrument played by rubbing glass or crystal goblets or bowls. The alternate instrument consisting of a set of wine glasses (usually tuned with water) is generally known in English as “musical glasses” or the “glass harp”.

When Benjamin Franklin invented his mechanical version of the instrument in 1761, he called it the armonica, based on the Italian word armonia, which means “harmony”. The unrelated free-reed wind instrument aeolina, today called the “harmonica”, was not invented until 1821, sixty years later.

The word “hydrodaktulopsychicharmonica” is also recorded, composed of Greek roots to mean something like “harmonica to produce music for the soul by fingers dipped in water” (hydro- for “water”, daktul- for “finger”, psych- for “soul”). The Oxford Companion to Music mentions that this word is “the longest section of the Greek language ever attached to any musical instrument, for a reader of The Times wrote to that paper in 1932 to say that in his youth he heard a performance of the instrument where it was called a hydrodaktulopsychicharmonica.” The Museum of Music in Paris displays a hydrodaktulopsychicharmonica.


Because its sounding portion is made of glass, the glass harmonica is a type of crystallophone. The phenomenon of rubbing a wet finger around the rim of a wine goblet to produce tones is documented back to Renaissance times; Galileo considered the phenomenon (in his Two New Sciences), as did Athanasius Kircher.

The Irish musician Richard Pockrich is typically credited as the first to play an instrument composed of glass vessels (glass harp) by rubbing his fingers around the rims. Beginning in the 1740s, he performed in London on a set of upright goblets filled with varying amounts of water. His career was cut short by a fire in his room, which killed him and destroyed his apparatus.

Edward Delaval, a friend of Benjamin Franklin and a fellow of the Royal Society, extended the experiments of Pockrich, contriving a set of glasses better tuned and easier to play. During the same decade, Christoph Willibald Gluck also attracted attention playing a similar instrument in England.

Franklin’s armonica


A modern glass armonica built using Benjamin Franklin’s design

Benjamin Franklin invented a radically new arrangement of the glasses in 1761 after seeing water-filled wine glasses played by Edmund Delaval at Cambridge in England in May 1761. Franklin worked with London glassblower Charles James to build one, and it had its world premiere in early 1762, played by Marianne Davies.

Writing to his friend Giambatista Beccaria in Turin, Italy, Franklin wrote from London in 1762 about his musical instrument: “The advantages of this instrument are, that its tones are incomparably sweet beyond those of any other; that they may be swelled and softened at pleasure by stronger or weaker pressures of the finger, and continued to any length; and that the instrument, being well tuned, never again wants tuning. In honour of your musical language, I have borrowed from it the name of this instrument, calling it the Armonica.”

In Franklin’s treadle-operated version, 37 bowls were mounted horizontally on an iron spindle. The whole spindle turned by means of a foot pedal. The sound was produced by touching the rims of the bowls with water-moistened fingers. Rims were painted different colors according to the pitch of the note: A (dark blue), B (purple), C (red), D (orange), E (yellow), F (green), G (blue), and accidentals were marked in white. With the Franklin design, it is possible to play ten glasses simultaneously if desired, a technique that is very difficult if not impossible to execute using upright goblets. Franklin also advocated the use of a small amount of powdered chalk on the fingers, which under some acidic water conditions helped produce a clear tone.

Some attempted improvements on the armonica included adding keyboards, placing pads between the bowls to reduce sympathetic vibrations, and using violin bows. Another supposed improvement claimed in ill-informed post-period observations of non-playing instruments was to have the glasses rotate into a trough of water. However, William Zeitler put this idea to the test by rotating an armonica cup into a basin of water; the water has the same effect as putting water in a wine glass – it changes the pitch. With several dozen glasses, each a different diameter and thus rotating with a different depth, the result would be musical cacophony. This modification also made it much harder to make the glass “speak”, and muffled the sound.

In 1975, an original armonica was acquired by the Bakken Museum in Minneapolis and put on display, albeit without its original glass bowls (they were destroyed during shipment). It was purchased through a musical instrument dealer in France, from the descendants of Mme. Brillon de Jouy, a neighbor of Benjamin Franklin’s from 1777 to 1785, when he lived in the Paris suburb of Passy. Some 18th- and 19th-century specimens of the armonica have survived into the 21st century. Franz Mesmer also played the armonica and used it as an integral part of his Mesmerism.

An original Franklin armonica is in the archives at the Franklin Institute in Philadelphia, having been donated in 1956 by Franklin’s descendants after “the children took great delight in breaking the bowls with spoons” during family gatherings. It is only placed on display for special occasions, such as Franklin’s birthday. The Franklin Institute is also the home of the Benjamin Franklin National Memorial.

A website has attempted to catalog publicly known Franklin-era glass armonicas. The Museum of Fine Arts, Boston has an early 19th-century instrument on display, which is occasionally used for public performances and recordings.

Musical works


Part of the original manuscript score of “Aquarium” from The Carnival of the Animals by Camille Saint-Saëns. The top staff was written for the (glass) “Harmonica”. About this sound Play (help·info)

Composers including J. G. Naumann, Padre Martini, Johann Adolph Hasse, Baldassare Galuppi, and Niccolò Jommelli, and more than 100 others composed works for the glass harmonica;   some pieces survive in the repertoire through transcriptions for more conventional instruments. European monarchs indulged in playing it, and even Marie Antoinette took lessons as a child from Franz Anton Mesmer.

Wolfgang Amadeus Mozart wrote his 1791 K. 617 and K.356 (K.617a) for the glass harmonica. Ludwig van Beethoven used the instrument in an 1814 melodrama Leonore Prohaska. Gaetano Donizetti used the instrument in the accompaniment to Amelia’s aria “Par che mi dica ancora” in Il castello di Kenilworth, premiered in 1829. He also originally specified the instrument in Lucia di Lammermoor (1835) as a haunting accompaniment to the heroine’s “mad scenes”, though before the premiere he was required by the producers to rewrite the part for two flutes. Camille Saint-Saëns used this instrument in his 1886 The Carnival of the Animals (in movements 7 and 14). Richard Strauss used the instrument in his 1917 Die Frau ohne Schatten.

For a while the instrument was “extraordinarily popular,” its “‘ethereal” qualities characteristic, along with instruments such as the nail violin and Aeolian harp, of Empfindsamkeit, but “the instrument fell into oblivion,” around 1830. Since the armonica’s performance revival during the 1980s, composers have again written for it (solo, chamber music, opera, electronic music, popular music) including Jan Erik Mikalsen, Regis Campo, Etienne Rolin, Philippe Sarde, Damon Albarn, Tom Waits, Michel Redolfi, Cyril Morin, Stefano Giannotti, Thomas Bloch, Jörg Widmann (Armonica 2006), and Guillaume Connesson.

The music for the 1997 ballet Othello by American composer Elliot Goldenthal opens and closes with the glass harmonica. The ballet was performed at San Francisco Ballet, the American Ballet Theater, the Joffrey Ballet, and on tour in Europe including at the Opera Garnier with Dennis James performing with his historical replica instrument.

George Benjamin’s opera Written on Skin, which premiered at the 2012 Aix-en-Provence Festival, includes a prominent and elaborate part for the glass harmonica..

Purported dangers

The instrument’s popularity did not last far beyond the 18th century. Some claim this was due to strange rumors that using the instrument caused both musicians and their listeners to go mad. It is a matter of conjecture how pervasive that belief was; all the commonly cited examples of this rumor seems to be German, if not confined to Vienna. One example of alleged effects from playing the glass harmonica was noted by a German musicologist Friedrich Rochlitz in the Allgemeine Musikalische Zeitung:

The harmonica excessively stimulates the nerves, plunges the player into a nagging depression and hence into a dark and melancholy mood that is apt method for slow self-annihilation. If you are suffering from any kind of nervous disorder, you should not play it; if you are not yet ill you should not play it; if you are feeling melancholy you should not play it.

Marianne Davies, who played flute and harpsichord – and was a young woman said to be related to Franklin – became proficient enough at playing the armonica to offer public performances. After touring for many years in duo performances with her celebrated vocalist sister, she was also said to have been afflicted with a melancholia attributed to the plaintive tones of the instrument. Marianne Kirchgessner was an armonica player; she died at the age of 39 of pneumonia or an illness much like it. However many others, including Franklin, lived long lives.

For a time the armonica achieved a genuine vogue, but like most fads, that for the armonica eventually passed. It has been claimed the sound-producing mechanism did not generate sufficient power to fill the large halls that were becoming home to modern stringed instruments, brass, woodwinds, and percussion. That the instrument was made with glass, and subject to easy breakage, perhaps did not help either. By 1820, the armonica had mostly disappeared from frequent public performance, perhaps because musical fashions were changing.

A modern version of the “purported dangers” claims that players suffered lead poisoning because armonicas were made of lead glass. However, there is no known scientific basis for the theory that merely touching lead glass can cause lead poisoning. Lead poisoning was common in the 18th and early 19th centuries for both armonica players and non-players alike; doctors prescribed lead compounds for a long list of ailments, and lead or lead oxide was used as a food preservative and in cookware and eating utensils. Trace amounts of lead that armonica players in Franklin’s day received from their instruments would likely have been dwarfed by lead from other sources, such as the lead-content paint used to mark visual identification of the bowls to the players.

Historical replicas by Eisch use so-called “White Crystal” developed in the 18th c. replacing the lead with a higher potash content; many modern newly invented devices, such as those made by Finkenbeiner, are made from so-called Quartz “pure silica glass” – a glass formulation developed in the early 20th c. for scientific purposes.

Perception of the sound

The somewhat disorienting quality of the ethereal sound is due in part to the way that humans perceive and locate ranges of sounds. Above 4 kHz people primarily use the loudness of the sound to differentiate between left and right ears and thus triangulate, or locate the source. Below 1 kHz, they use the phase differences of sound waves arriving at their left and right ears to identify location. The predominant pitch of the armonica is in the range of 1–4 kHz, which coincides with the sound range where the brain is “not quite sure”, and thus listeners have difficulty locating it in space (where it comes from), and discerning the source of the sound (the materials and techniques used to produce it).

Benjamin Franklin himself described the armonica’s tones as “incomparably sweet”. The full quotation, written in a letter to Giambattista Beccaria, an Italian priest and electrician, is: “The advantages of this instrument are that its tones are incomparably sweet beyond those of any other; that they may be swelled and softened at pleasure by stronger or weaker pressures of the finger, and continued to any length; and that the instrument, once well tuned, never again wants tuning.”

A music critic for the Morning Chronicle, writing of a performance by Kirchgessner in 1794, said, “Her taste is chastened and the dulcet notes of the instrument would be delightful indeed, were they more powerful and articulate; but that we believe the most perfect execution cannot make them. In a smaller room and an audience less numerous, the effect must be enchanting. Though the accompaniments were kept very much under, they were still occasionally too loud.”

Modern revival


Dennis James plays the armonica at the Poncan Theatre in Ponca City, Oklahoma, on April 2, 2011.

Music for glass harmonica was all-but-unknown from 1820 until the 1930s (although Gaetano Donizetti intended for the aria “Il dolce suono” from his 1835 opera Lucia di Lammermoor to be accompanied by a glass armonica, and Richard Strauss specified use of the instrument in his 1919 opera Die Frau ohne Schatten), when German virtuoso Bruno Hoffmann began revitalizing interest in his individual goblet instrument version that he named the glass harp for his stunning performances. Playing his “glass harp” (with Eisch manufactured custom designed glasses mounted in a case designed with underlying resonance chamber) he transcribed or rearranged much of the literature written for the mechanized instrument, and commissioned contemporary composers to write new pieces for his goblet version.

Franklin’s glass armonica design was reworked yet again without patent credit by master glassblower and musician, Gerhard B. Finkenbeiner (1930–1999) in 1984. After thirty years of experimentation, Finkenbeiner’s imitative prototype consisted of clear glasses and glasses later equipped with gold bands mimicking late 18th-century designs. The historical instruments with gold bands indicated the equivalent of the black keys on the piano, simplifying the multi-hued painted bowl rims with white accidentals as specified by Franklin. Finkenbeiner Inc., of Waltham, Massachusetts, continues to produce versions of these instruments commercially as of 2014, featuring glass elements made of scientific formulated fused-silica quartz.

French instrument makers and artists Bernard and François Baschet invented a modern variation of the Chladni Euphone in 1952, the “crystal organ” or Cristal di Baschet, which consists of up to 52 chromatically tuned resonating metal rods that are set into motion by attached glass rods that are rubbed with wet fingers. The Cristal di Baschet differs mainly from the other glass instruments in that the identical length and thickness glass rods are set horizontally, and attach to the tuned metal stems that have added metal blocks for increasing resonance. The result is a fully acoustic instrument, and impressive amplification obtained using fiberglass or metal cones fixed on wood and by a tall cut-out multi-resonant metal part in the shape of a flame. Some thin added metallic wires resembling cat whiskers are placed under the instrument, supposedly to increase the sound power of high-pitched frequencies.

Dennis James recorded an album of all glass music, Cristal: Glass Music Through the Ages co-produced by Linda Ronstadt and Grammy Award-winning producer John Boylan. James plays the glass harmonica, the Cristal di Baschet, and the Seraphim on the CD in original historical compositions and new arrangements for glass by Mozart, Scarlatti, Schnaubelt, and Fauré and collaborates on the recording with the Emerson String Quartet, operatic soprano Ruth Ann Swenson, and Ronstadt. James played glass instruments on Marco Beltrami’s film scores for The Minus Man (1999) and The Faculty (1998). “I first became aware of glass instruments at about the age of 6 while visiting the Franklin Institute in Philadelphia. I can still recall being mesmerized by the appearance of the original Benjamin Franklin armonica then on display in its own showcase in the entry rotunda of the city’s famed science museum.” James Horner used a glass harmonica and pan flute for Spock’s theme in the 1982 film Star Trek II: The Wrath of Khan.

Notable players


  • Marie Antoinette
  • Marianne Davies
  • Benjamin Franklin (United States)
  • Franz Mesmer
  • Marianne Kirchgessner
  • Mrs. Philip Thicknesse (born Anne Ford), 1775, United Kingdom)


  • Thomas Bloch (France)
  • Cecilia Brauer (United States)
  • Bill Hayes (New York City) Broadway Musician and Percussionist, Barbra Streisand Orchestra 1994, 2006, 2007
  • Martin Hilmer (Germany)
  • Bruno Hoffmann (Germany)
  • Dennis James (United States)
  • Alasdair Malloy (United Kingdom)
  • David Mauldin (United States)
  • Gloria Parker (United States) glass harp
  • Gerald Schönfeldinger (Austria)
  • Dean Shostak (United States)
  • Ed Stander (United States)
  • William Zeitler (United States)

Related instruments


An armonica

Another instrument that is also played with wet fingers is the hydraulophone.   The hydraulophone sounds similar to a glass armonica but has a darker, heavier sound, that extends down into the subsonic range. The technique for playing the hydraulophone is similar to that used for playing the armonica.