The Gruppenhorchgerät ('group listening device', abbreviated GHG) was a hydrophone array which was used on vessels of the German Kriegsmarine in World War II .
54-526: In World War I carbon microphones were still used as sound receivers. The individual receivers were mostly placed in the front part of the vessel along the hull sides to have enough distance from the screw and the noise they emitted. The individual microphones were arranged in groups and each was oriented in a different direction. The individual microphones had to be connected manually to take bearings. They were not very reliable, so other transducers were experimented with. Dynamic microphones were also discarded. At
108-560: A continuous wave from an Alexanderson alternator was fed directly to the transmitting antenna through a water-cooled carbon microphone. Later systems using vacuum tube oscillators often used the output from a carbon microphone to modulate the grid bias of the oscillator or output tube to achieve modulation. Apart from legacy telephone installations in various conditions according to areas and countries, carbon microphones may be still used today in certain niche applications although manufacturers are discontinuing distribution. For example,
162-401: A modulation of the current, creating a varying electric current that reproduces the varying pressure of the sound wave. In telephony , this undulating current is directly passed through the telephone wires to the central office . In public address systems it is amplified by an audio amplifier . The frequency response of most carbon microphones, however, is limited to a narrow range, and
216-531: A fairly high noise level, led to their abandonment in those applications by the late 1920s. They continued to be widely used for low-end public address, and military and amateur radio applications for some decades afterward. The first microphone that enabled proper voice telephony was the (loose-contact) carbon microphone (then called transmitter). This was independently developed around 1878 by David Edward Hughes in England and Emile Berliner and Thomas Edison in
270-423: A power gain. This can readily be demonstrated by connecting a battery, microphone and earphone in series. If the microphone and earphone are brought in contact the system will oscillate. This is only possible if the power gain around the loop is greater than unity. The microphone's low-voltage performance is particularly useful in remote locations served by very long telephone lines, where the electrical resistance of
324-461: A relatively accurate electrical reproduction of the sound signal. Hughes also coined the word microphone. He demonstrated his apparatus to the Royal Society by magnifying the sound of insects scratching through a sound box. Contrary to Edison, Hughes decided not to take out a patent; instead, he made his invention a gift to the world. In America, Edison and Berliner fought a long legal battle over
378-473: A sense of community. In The Social Construction of Mobile Telephony it is suggested that each phone call and text message is more than an attempt to converse. Instead, it is a gesture which maintains the social network between family and friends. Although there is a loss of certain social cues through telephones, mobile phones bring new forms of expression of different cues that are understood by different audiences. New language additives attempt to compensate for
432-419: A separate telephone wired to each locations to be reached. This quickly became inconvenient and unmanageable when users wanted to communicate with more than a few people. The invention of the telephone exchange provided the solution for establishing telephone connections with any other telephone in service in the local area. Each telephone was connected to the exchange at first with one wire, later one wire pair,
486-535: A switching matrix in the main unit. The sonar operator could determine the ship's side and the exact direction of the sound source. To improve the resolution, there were three switchable crossover with 1, 3 and 6 kHz center frequency. A disadvantage of the side mounting, was a dead zone of 40 ° to fore and aft. Range: 20 km to individual drivers, 100 km against Convoy Search area: 2 × 140 ° Resolution: <1 ° at 6 kHz, 1.5 ° for 3 kHz, 4 ° for 1 kHz; without crossover 8 ° In August 1941 U 570
540-544: A system of telecommunications in which telephonic equipment is employed in the transmission of speech or other sound between points, with or without the use of wires. The term is also used frequently to refer to computer hardware , software , and computer network systems, that perform functions traditionally performed by telephone equipment. In this context the technology is specifically referred to as Internet telephony, or voice over Internet Protocol (VoIP). The first telephones were connected directly in pairs. Each user had
594-508: A trunk to a distant exchange. Most of the exchanges in the world are interconnected through a system of larger switching systems, forming the public switched telephone network (PSTN). In the second half of the 20th century, fax and data became important secondary applications of the network created to carry voices, and late in the century, parts of the network were upgraded with ISDN and DSL to improve handling of such traffic. Today, telephony uses digital technology ( digital telephony ) in
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#1732856196715648-439: Is a major development in the evolution of office automation. The term is used in describing the computerized services of call centers, such as those that direct your phone call to the right department at a business you're calling. It is also sometimes used for the ability to use your personal computer to initiate and manage phone calls (in which case you can think of your computer as your personal call center). Digital telephony
702-456: Is also used on private networks which may or may not have a connection to the global telephone network. Direct person-to-person communication includes non-verbal cues expressed in facial and other bodily articulation, that cannot be transmitted in traditional voice telephony. Video telephony restores such interactions to varying degrees. Social Context Cues Theory is a model to measure the success of different types of communication in maintaining
756-546: Is relatively unregulated by government. In the United States, the Federal Communications Commission (FCC) regulates phone-to-phone connections, but says they do not plan to regulate connections between a phone user and an IP telephony service provider. A specialization of digital telephony, Internet Protocol (IP) telephony involves the application of digital networking technology that was the foundation to
810-422: Is the field of technology involving the development, application, and deployment of telecommunications services for the purpose of electronic transmission of voice, fax , or data , between distant parties. The history of telephony is intimately linked to the invention and development of the telephone . Telephony is commonly referred to as the construction or operation of telephones and telephonic systems and as
864-455: Is the use of digital electronics in the operation and provisioning of telephony systems and services. Since the late 20th century, a digital core network has replaced the traditional analog transmission and signaling systems, and much of the access network has also been digitized. Starting with the development of transistor technology, originating from Bell Telephone Laboratories in 1947, to amplification and switching circuits in
918-447: Is very thin and faces toward the speaking person, acting as a diaphragm . Sound waves striking the diaphragm cause it to vibrate, exerting a varying pressure on the granules, which in turn changes the electrical resistance between the plates. Higher pressure lowers the resistance as the granules are pushed closer together. A steady direct current is passed between the plates through the granules. The varying resistance results in
972-507: Is well known, Wiesenfeld, Raghuram, and Garud point out that there is a value and efficiency to the type of communication for different tasks. They examine work places in which different types of communication, such as the telephone, are more useful than face-to-face interaction. The expansion of communication to mobile telephone service has created a different filter of the social cues than the land-line telephone. The use of instant messaging, such as texting , on mobile telephones has created
1026-1166: The Internet to create, transmit, and receive telecommunications sessions over computer networks . Internet telephony is commonly known as voice over Internet Protocol (VoIP), reflecting the principle, but it has been referred with many other terms. VoIP has proven to be a disruptive technology that is rapidly replacing traditional telephone infrastructure technologies. 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 . IP telephony uses an Internet connection and hardware IP phones , analog telephone adapters, or softphone computer applications to transmit conversations encoded as data packets . In addition to replacing plain old telephone service (POTS), IP telephony services compete with mobile phone services by offering free or lower cost connections via WiFi hotspots . VoIP
1080-480: The Seignette crystal , which is formed from a mixture of different salts. From 1935 crystal receivers were permanently installed on all German submarines. Modern submarines still use electrostriction and barium titanate converters today. The GHG for U-boats consisted of two groups of 24 sensors (one group on each side of the ship). Each sensor had a tube preamplifier. These 48 low frequency signals were then routed to
1134-451: The Shure 104c, was still in demand in the late 2010s because of its wide compatibility with existing equipment. The principal advantage of carbon microphones over other microphone designs is that they can produce high-level audio signals from very low DC voltages, without needing any form of additional amplification or batteries. The carbon microphone, by virtue of using a power supply, gives
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#17328561967151188-401: The local loop . Nearby exchanges in other service areas were connected with trunk lines , and long-distance service could be established by relaying the calls through multiple exchanges. Initially, exchange switchboards were manually operated by an attendant, commonly referred to as the " switchboard operator ". When a customer cranked a handle on the telephone, it activated an indicator on
1242-478: The modified discrete cosine transform (MDCT), has been widely adopted for speech coding in voice-over-IP (VoIP) applications since the late 1990s. The development of transmission methods such as SONET and fiber optic transmission further advanced digital transmission. Although analog carrier systems existed that multiplexed multiple analog voice channels onto a single transmission medium, digital transmission allowed lower cost and more channels multiplexed on
1296-410: The rapid scaling and miniaturization of MOS technology. Uncompressed PCM digital audio with 8-bit depth and 8 kHz sample rate requires a bit rate of 64 kbit/s , which was impractical for early digital telecommunication networks with limited network bandwidth . A solution to this issue was linear predictive coding (LPC), a speech coding data compression algorithm that
1350-511: The 1930s in portable audio equipment such as hearing aids. The Western Electric 65A carbon amplifier was 1.2" in diameter and 0.4" high and weighed less than 1.4 ounces. Such carbon amplifiers did not require the heavy bulky batteries and power supplies used by vacuum tube amplifiers. By the 1950s, carbon amplifiers for hearing aids had been replaced by miniature vacuum tubes (only to be shortly replaced by transistors). However, carbon amplifiers are still being produced and sold. An illustration of
1404-493: The 1950s, the public switched telephone network (PSTN) has gradually moved towards solid-state electronics and automation . Following the development of computer -based electronic switching systems incorporating metal–oxide–semiconductor (MOS) and pulse-code modulation (PCM) technologies, the PSTN gradually evolved towards the digitization of signaling and audio transmissions . Digital telephony has since dramatically improved
1458-591: The GHG typ 57 manufactured by Atlas, Bremen. It consisted of 60 crystal microphones and had a typical range of between four and six kilometers, although in most favourable circumstances a range of 40 kilometers was possible. Carbon microphone The carbon microphone , also known as carbon button microphone , button microphone , or carbon transmitter , is a type of microphone , a transducer that converts sound to an electrical audio signal . It consists of two metal plates separated by granules of carbon . One plate
1512-623: The MOS mixed-signal integrated circuit , which combines analog and digital signal processing on a single chip, developed by former Bell engineer David A. Hodges with Paul R. Gray at UC Berkeley in the early 1970s. In 1974, Hodges and Gray worked with R.E. Suarez to develop MOS switched capacitor (SC) circuit technology, which they used to develop a digital-to-analog converter (DAC) chip, using MOS capacitors and MOSFET switches for data conversion. MOS analog-to-digital converter (ADC) and DAC chips were commercialized by 1974. MOS SC circuits led to
1566-466: The US. Although Edison was awarded the first patent in mid-1877, Hughes had demonstrated his working device in front of many witnesses some years earlier, and most historians credit him with its invention. Hughes' device used loosely packed carbon granules - the varying pressure exerted on the granules by the diaphragm from the acoustic waves caused the resistance of the carbon to vary proportionally, allowing
1620-416: The advent of new communication technologies. Telephony now includes the technologies of Internet services and mobile communication, including video conferencing. The new technologies based on Internet Protocol (IP) concepts are often referred to separately as voice over IP (VoIP) telephony, also commonly referred to as IP telephony or Internet telephony. Unlike traditional phone service, IP telephony service
1674-405: The amplification provided by carbon microphones was the oscillation caused by feedback, which resulted in an audible squeal from the old " candlestick telephone " if its earphone was placed near the carbon microphone. Early AM radio transmitters relied on carbon microphones for voice modulation of the radio signal. In the first long-distance audio transmissions by Reginald Fessenden in 1906,
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1728-459: The assistance of other operators at other exchangers in the network. Until the 1970s, most telephones were permanently wired to the telephone line installed at customer premises. Later, conversion to installation of jacks that terminated the inside wiring permitted simple exchange of telephone sets with telephone plugs and allowed portability of the set to multiple locations in the premises where jacks were installed. The inside wiring to all jacks
1782-399: The bandwidth-limited analog voice signal and encoding using pulse-code modulation (PCM). Early PCM codec - filters were implemented as passive resistor – capacitor – inductor filter circuits, with analog-to-digital conversion (for digitizing voices) and digital-to-analog conversion (for reconstructing voices) handled by discrete devices . Early digital telephony was impractical due to
1836-422: The board in front of the operator, who would in response plug the operator headset into that jack and offer service. The caller had to ask for the called party by name, later by number, and the operator connected one end of a circuit into the called party jack to alert them. If the called station answered, the operator disconnected their headset and completed the station-to-station circuit. Trunk calls were made with
1890-420: The capacity, quality and cost of the network. Digitization allows wideband voice on the same channel, with improved quality of a wider analog voice channel. The earliest end-to-end analog telephone networks to be modified and upgraded to transmission networks with Digital Signal 1 (DS1/T1) carrier systems date back to the early 1960s. They were designed to support the basic 3 kHz voice channel by sampling
1944-429: The critical level. In particular, this means that one telephone on a " party line " may tend to "hog" all the line current , cutting the others off. With carbon microphones, all receivers on the same line will still operate, albeit with reduced output . Carbon microphones are also widely used in safety-critical applications such as mining and chemical manufacturing , where higher line voltages cannot be used, due to
1998-1115: The development of PCM codec-filter chips in the late 1970s. The silicon-gate CMOS (complementary MOS) PCM codec-filter chip, developed by Hodges and W.C. Black in 1980, has since been the industry standard for digital telephony. By the 1990s, telecommunication networks such as the public switched telephone network (PSTN) had been largely digitized with very-large-scale integration (VLSI) CMOS PCM codec-filters, widely used in electronic switching systems for telephone exchanges , private branch exchanges (PBX) and key telephone systems (KTS); user-end modems ; data transmission applications such as digital loop carriers , pair gain multiplexers , telephone loop extenders , integrated services digital network (ISDN) terminals, digital cordless telephones and digital cell phones ; and applications such as speech recognition equipment, voice data storage , voice mail and digital tapeless answering machines . The bandwidth of digital telecommunication networks has been rapidly increasing at an exponential rate, as observed by Edholm's law , largely driven by
2052-736: The device produces significant electrical noise . Before the proliferation of vacuum tube amplifiers in the 1920s, carbon microphones were the only practical means of obtaining high-level audio signals. They were widely used in telephone systems until the 1980s, while other applications used different microphone designs much earlier. Their low cost, inherently high output and frequency response characteristic were well suited for telephony. For plain old telephone service (POTS), carbon-microphone based telephones can still be used without modification. Carbon microphones, usually modified telephone transmitters, were widely used in early AM radio broadcasting systems, but their limited frequency response, as well as
2106-698: The end of the process, the piezoelectric principle was deemed the most suitable. This was discovered by Pierre Curie in 1880. The quartz crystals generate electric voltage depending on the pressure acting on it. In collaboration with the Imperial German Navy , Atlas Werke AG in Bremen and Electroacustik (ELAC) in Kiel worked on piezoelectric transducers and the development of detectors and amplifiers in general. They experimented with different kinds of crystals, or combinations of several of them. The best result rendered
2160-455: The first transistors in which drain and source were adjacent at the surface. Subsequently, a team demonstrated a working MOSFET at Bell Labs 1960. MOS technology was initially overlooked by Bell because they did not find it practical for analog telephone applications, before it was commercialized by Fairchild and RCA for digital electronics such as computers . MOS technology eventually became practical for telephone applications with
2214-400: The low performance and high costs of early PCM codec-filters. Practical digital telecommunication was enabled by the invention of the metal–oxide–semiconductor field-effect transistor (MOSFET), which led to the rapid development and wide adoption of PCM digital telephony. In 1957, Frosch and Derick were able to manufacture the first silicon dioxide field effect transistors at Bell Labs,
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2268-433: The non-verbal cues present in face-to-face interactions. The research examines many different cues, such as the physical context, different facial expressions, body movements, tone of voice, touch and smell. Various communication cues are lost with the usage of the telephone. The communicating parties are not able to identify the body movements, and lack touch and smell. Although this diminished ability to identify social cues
2322-474: The patent rights. Ultimately a federal court awarded Edison full rights to the invention, stating "Edison preceded Berliner in the transmission of speech...The use of carbon in a transmitter is, beyond controversy, the invention of Edison" and the Berliner patent was ruled invalid. The carbon microphone is the direct prototype of today's microphones and was critical in the development of telephony, broadcasting and
2376-488: The provisioning of telephone services and systems. Telephone calls can be provided digitally, but may be restricted to cases in which the last mile is digital, or where the conversion between digital and analog signals takes place inside the telephone. This advancement has reduced costs in communication, and improved the quality of voice services. The first implementation of this, ISDN , permitted all data transport from end-to-end speedily over telephone lines. This service
2430-446: The recording industries. Later, carbon granules were used between carbon buttons. Carbon microphones were widely used in telephones from 1890 until the 1980s. Carbon microphones can be used as amplifiers . This capability was used in early telephone repeaters , making long-distance phone calls possible in the era before vacuum tube amplifiers. In these repeaters, a magnetic telephone receiver (an electrical-to-mechanical transducer )
2484-452: The risk of sparking and consequent explosions . Carbon-based telephone systems are also resistant to damage from high- voltage transients , such as those produced by lightning strikes, and electromagnetic pulses of the type generated by nuclear explosions , and so are still maintained as backup communication systems in critical military installations. Telephony Telephony ( / t ə ˈ l ɛ f ə n i / tə- LEF -ə-nee )
2538-465: The transmission medium. Today the end instrument often remains analog but the analog signals are typically converted to digital signals at the serving area interface (SAI), central office (CO), or other aggregation point. Digital loop carriers (DLC) and fiber to the x place the digital network ever closer to the customer premises, relegating the analog local loop to legacy status. The field of technology available for telephony has broadened with
2592-424: The wires can lead to severe DC voltage drop. Most all-electronic telephones need at least three volts DC to work, and so will often become useless in such situations, whereas carbon transmitter telephones will continue to work down to a fraction of a volt. Even where they do work, electronic telephones also suffer from the so-called " cliff effect ", whereby they abruptly stop working when the line voltage falls below
2646-557: Was captured by the British Royal Navy . Only in May 1942 the submarine’s ELAC equipment was thoroughly analyzed; the above resolution values were determined. The GHG could not be used whilst cruising on the surface, and it could not effectively at periscope depth. The optimum operating modus was at a depth below 20 meter with a reduced speed of less than 3 knots. To solve this, a new listening device, known as Balkongerät ('balcony-device')
2700-417: Was connected in one place to the wire drop which connects the building to a cable. Cables usually bring a large number of drop wires from all over a district access network to one wire center or telephone exchange. When a telephone user wants to make a telephone call , equipment at the exchange examines the dialed telephone number and connects that telephone line to another in the same wire center, or to
2754-461: Was developed. It was mounted at the front and the bottom of a submarine, so it had less interference from surface noise. There was however now a dead zone towards the rear of the submarine. The Balkongerät was successfully tested on U-194 in January 1943. It was installed on some small Type VII submarine and was standard on the new large Type XXI submarine German Capital ships were equipped with
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#17328561967152808-451: Was first proposed by Fumitada Itakura of Nagoya University and Shuzo Saito of Nippon Telegraph and Telephone (NTT) in 1966. LPC was capable of audio data compression down to 2.4 kbit/s, leading to the first successful real-time conversations over digital networks in the 1970s. LPC has since been the most widely used speech coding method. Another audio data compression method, a discrete cosine transform (DCT) algorithm called
2862-514: Was later made much less important due to the ability to provide digital services based on the Internet protocol suite . Since the advent of personal computer technology in the 1980s, computer telephony integration (CTI) has progressively provided more sophisticated telephony services, initiated and controlled by the computer, such as making and receiving voice, fax, and data calls with telephone directory services and caller identification . The integration of telephony software and computer systems
2916-507: Was mechanically coupled to a carbon microphone. Because a carbon microphone works by varying a current passed through it, instead of generating a signal voltage as with most other microphone types, this arrangement could be used to boost weak signals and send them down the line. These amplifiers were mostly abandoned with the development of vacuum tubes , which offered higher gain and better sound quality . Even after vacuum tubes were in common use, carbon amplifiers continued to be used during
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