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- Bell_202_modem abstract "The Bell 202 modem was an early modem standard developed by Bell System. It specifies audio frequency-shift keying (AFSK) to encode and transfer data at a rate of 1200 bits per second, half-duplex (one-way). 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.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 This modulation standard was retained until around 2000, when it was superseded by faster FSK and PSK modulation methods, although it is still utilised for extension of existing control systems that are already configured for this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.".
- Bell_202_modem wikiPageExternalLink bell202_en.html.
- Bell_202_modem wikiPageID "1414302".
- Bell_202_modem wikiPageLength "2890".
- Bell_202_modem wikiPageOutDegree "23".
- Bell_202_modem wikiPageRevisionID "662506884".
- Bell_202_modem wikiPageWikiLink AX.25.
- Bell_202_modem wikiPageWikiLink Amateur_radio.
- Bell_202_modem wikiPageWikiLink Automatic_Packet_Reporting_System.
- Bell_202_modem wikiPageWikiLink Bell_103_modem.
- Bell_202_modem wikiPageWikiLink Bell_System.
- Bell_202_modem wikiPageWikiLink Caller_ID.
- Bell_202_modem wikiPageWikiLink Category:Modems.
- Bell_202_modem wikiPageWikiLink Data_rate_units.
- Bell_202_modem wikiPageWikiLink Data_signaling_rate.
- Bell_202_modem wikiPageWikiLink Duplex_(telecommunications).
- Bell_202_modem wikiPageWikiLink Frequency-shift_keying.
- Bell_202_modem wikiPageWikiLink High_frequency.
- Bell_202_modem wikiPageWikiLink ITU-T.
- Bell_202_modem wikiPageWikiLink ITU_V.23.
- Bell_202_modem wikiPageWikiLink Manchester_code.
- Bell_202_modem wikiPageWikiLink Modem.
- Bell_202_modem wikiPageWikiLink North_America.
- Bell_202_modem wikiPageWikiLink Packet_radio.
- Bell_202_modem wikiPageWikiLink Plain_old_telephone_service.
- Bell_202_modem wikiPageWikiLink Production_control.
- Bell_202_modem wikiPageWikiLink Public_switched_telephone_network.
- Bell_202_modem wikiPageWikiLink Very_high_frequency.
- Bell_202_modem wikiPageWikiLinkText "BELL 202".
- Bell_202_modem wikiPageWikiLinkText "Bell 202 modem".
- Bell_202_modem wikiPageWikiLinkText "Bell 202 tones".
- Bell_202_modem wikiPageWikiLinkText "Bell 202".
- Bell_202_modem wikiPageUsesTemplate Template:Digital_modes.
- Bell_202_modem wikiPageUsesTemplate Template:Reflist.
- Bell_202_modem wikiPageUsesTemplate Template:Unreferenced.
- Bell_202_modem subject Category:Modems.
- Bell_202_modem type Protocol.
- Bell_202_modem comment "The Bell 202 modem was an early modem standard developed by Bell System. It specifies audio frequency-shift keying (AFSK) to encode and transfer data at a rate of 1200 bits per second, half-duplex (one-way). 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_modem label "Bell 202 modem".
- Bell_202_modem sameAs Q815673.
- Bell_202_modem sameAs Bell_202-Modem.
- Bell_202_modem sameAs Modem_Bell_202.
- Bell_202_modem sameAs m.04_l7l.
- Bell_202_modem sameAs Bell_202.
- Bell_202_modem sameAs Q815673.
- Bell_202_modem wasDerivedFrom Bell_202_modem?oldid=662506884.
- Bell_202_modem isPrimaryTopicOf Bell_202_modem.