The Bell 202 modem was an early (1976) modem standard developed by the Bell System. It specifies audio frequency-shift keying (AFSK) to encode and transfer data at a rate of 1200 bits per second, half-duplex. It has separate sets of circuits for 1200 bps and 300 bps rates. These signalling protocols, also used in third-party modems, are referred to generically as Bell 202 modulation, and any device employing it as Bell-202-compatible.
* Bell 202 AFSK uses a 1200 Hz tone for mark (typically a binary 1) and 2200 Hz for space (typically a binary 0).
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| - Bell 202-Modem (de)
- Bell 202 modem (en)
- Modem Bell 202 (fr)
- Bell 202 (ru)
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| - Bell 202 — модем и протокол модемной связи. Разработан корпорацией .Использовался для дистанционной настройки телекоммуникационного оборудования и определения номера вызывающего абонента Caller_ID.Использует частотную модуляцию с частотным разделением каналов.Может работать в режимах:
* несимметричный дуплекс: прямой канал 1200 bps, обратный канал 5 bps
* несимметричный дуплекс: прямой канал 1200 bps, обратный канал 150 bps
* полудуплекс 1200 bps. Логическую единицу (MARK) кодирует гармонической частотой 1200Гц.Логический ноль (SPACE) кодирует гармонической частотой 2200Гц. (ru)
- The Bell 202 modem was an early (1976) modem standard developed by the Bell System. It specifies audio frequency-shift keying (AFSK) to encode and transfer data at a rate of 1200 bits per second, half-duplex. It has separate sets of circuits for 1200 bps and 300 bps rates. These signalling protocols, also used in third-party modems, are referred to generically as Bell 202 modulation, and any device employing it as Bell-202-compatible.
* Bell 202 AFSK uses a 1200 Hz tone for mark (typically a binary 1) and 2200 Hz for space (typically a binary 0). (en)
- Das Bell 202-Modem ist eines der ersten Modems, das von der Firma AT&T entwickelt wurde.Die Halbduplex-Übertragung erfolgt in einer Richtung mit 1200 bps (Bits pro Sekunde). Als Modulationsverfahren wird Frequency Shift Keying (FSK) verwendet. Eine digitale "1" wird mit der Frequenz 1,2 kHz (1200 Hz) und eine "0" wird mit der Frequenz 2,2 kHz (2200 Hz) dargestellt. Da diese Modemtechnik die erste der Art war, wurden die Bezeichnungen Bell 202 kompatibel bzw. Bell 202-Standard geprägt. (de)
- Le modem Bell 202 est l'un des premiers modèles de modems, développé par AT&T. Il utilise une modulation de type audio FSK (AFSK) pour transmettre ses données à 1200 bits par seconde en half-duplex. D'autres modems utilisent le même type de modulation (appelée généralement modulation Bell 202) : on parle de modems compatibles Bell 202, ou plus simplement de modems Bell 202. La tonalité mark est à 2 200 Hz, et la tonalité space à 1 200 Hz. (fr)
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| - The Bell 202 modem was an early (1976) modem standard developed by the Bell System. It specifies audio frequency-shift keying (AFSK) to encode and transfer data at a rate of 1200 bits per second, half-duplex. It has separate sets of circuits for 1200 bps and 300 bps rates. These signalling protocols, also used in third-party modems, are referred to generically as Bell 202 modulation, and any device employing it as Bell-202-compatible.
* Bell 202 AFSK uses a 1200 Hz tone for mark (typically a binary 1) and 2200 Hz for space (typically a binary 0). In North America, Bell 202 AFSK modulation is used to transmit Caller ID information over POTS lines in the public telephone network. It is also employed in some commercial settings. In addition, Bell 202 is the basis for the most commonly used physical layer for the HART Communication Protocol - a communication protocol widely used in the process industries. Surplus Bell 202 modems were used by amateur radio operators to construct the first packet radio stations, despite its low signalling speed. A modified Bell 202 AFSK modulation, a common physical layer for AX.25, remains the standard for amateur VHF operation in most areas. Notably, Automatic Packet Reporting System (APRS) transmissions are encoded this way on VHF. On HF, APRS uses Bell 103 modulation. The Bell 202 standard was adopted around 1980 as the communications standard for subsea oil and gas production control systems, pioneered by the then FSSL (Ferranti Subsea Systems Ltd.) Controls, a spin-out company from the former TRW - Ferranti joint venture in the UK. This modulation standard was retained until around 2000, when it was superseded by faster FSK and PSK modulation methods, although it is still utilised for extension of existing control systems that are already configured for this technique. The 202 standard permitted useful techniques such as multi-dropping of slave modems to allow multiple nodes to be connected to the host via a single modem channel. Other techniques have included superposition of signal on power conductors, and distances in excess of 80 km were achieved in subsea applications using these techniques. This has been enhanced through the use of Manchester encoding over the FSK link, to provide simple Modulo-2 RZ (return to Zero) bit error detection and suppression improvement over these long distances. (en)
- Das Bell 202-Modem ist eines der ersten Modems, das von der Firma AT&T entwickelt wurde.Die Halbduplex-Übertragung erfolgt in einer Richtung mit 1200 bps (Bits pro Sekunde). Als Modulationsverfahren wird Frequency Shift Keying (FSK) verwendet. Eine digitale "1" wird mit der Frequenz 1,2 kHz (1200 Hz) und eine "0" wird mit der Frequenz 2,2 kHz (2200 Hz) dargestellt. Da diese Modemtechnik die erste der Art war, wurden die Bezeichnungen Bell 202 kompatibel bzw. Bell 202-Standard geprägt. Der Kommunikationsstandard ITU V.23 definiert die gleiche Übertragungsart, ist aber zu Bell 202 inkompatibel, da andere Signalfrequenzen verwendet werden. (de)
- Le modem Bell 202 est l'un des premiers modèles de modems, développé par AT&T. Il utilise une modulation de type audio FSK (AFSK) pour transmettre ses données à 1200 bits par seconde en half-duplex. D'autres modems utilisent le même type de modulation (appelée généralement modulation Bell 202) : on parle de modems compatibles Bell 202, ou plus simplement de modems Bell 202. La tonalité mark est à 2 200 Hz, et la tonalité space à 1 200 Hz. En Amérique du Nord, la modulation Bell 202 est utilisée pour transmettre les informations du service de présentation du numéro (Caller ID) sur le réseau téléphonique commuté. Elle est également employée par des services commerciaux[réf. nécessaire]. Des modems Bell 202 réformés ont été utilisés par des radioamateurs pour construire les premiers équipements de packet radio. En dépit de son faible débit de transmission, la modulation Bell 202 reste le standard pour les transmissions de données entre radioamateurs en VHF dans la plupart des régions. Notamment, les transmissions APRS utilisent cette technique. (fr)
- Bell 202 — модем и протокол модемной связи. Разработан корпорацией .Использовался для дистанционной настройки телекоммуникационного оборудования и определения номера вызывающего абонента Caller_ID.Использует частотную модуляцию с частотным разделением каналов.Может работать в режимах:
* несимметричный дуплекс: прямой канал 1200 bps, обратный канал 5 bps
* несимметричный дуплекс: прямой канал 1200 bps, обратный канал 150 bps
* полудуплекс 1200 bps. Логическую единицу (MARK) кодирует гармонической частотой 1200Гц.Логический ноль (SPACE) кодирует гармонической частотой 2200Гц. (ru)
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