56 kbit/s line: Difference between revisions
imported>Bri m →See also: updated anchor |
imported>DareWhat? no reference template replaced, reference added |
||
| Line 1: | Line 1: | ||
{{Short description|Digital connection matching the data rate of a digital telephone line}} | {{Short description|Digital connection matching the data rate of a digital telephone line}}{{More citations needed|date=November 2025}} | ||
A '''56 kbit/s line''' is a digital connection capable of carrying 56 [[kilobit]]s per second ([[kbit/s]]), or 56,000 [[bit/s]], the [[data]] rate of a classical single channel [[digital telephone]] line in [[North America]]. Since the wide deployment of faster, cheaper technologies, 56 kbit/s lines are generally considered to be an [[obsolete]] technology. | A '''56 kbit/s line''' is a digital connection capable of carrying 56 [[kilobit]]s per second ([[kbit/s]]), or 56,000 [[bit/s]], the [[data]] rate of a classical single channel [[digital telephone]] line in [[North America]].<ref>{{Cite web |title=56k Page |url=https://www.laits.utexas.edu/~anorman/long.extra/Student.F98/modem/56k.htm |access-date=2025-11-07 |website=www.laits.utexas.edu}}</ref> Since the wide deployment of faster, cheaper technologies, 56 kbit/s lines are generally considered to be an [[obsolete]] technology.<ref>{{Cite web |title=What Is 56k Line? |url=https://www.computerhope.com/jargon/num/56kline.htm |access-date=2025-11-07 |website=Computer Hope |language=en}}</ref> | ||
==Speed derivation== | ==Speed derivation== | ||
The figure of 56 kbit/s is derived from its implementation using the same digital infrastructure used since the 1960s for [[digital telephony]] in the [[public switched telephone network]], which uses a [[sampling rate]] of 8,000 Hz for [[Pulse-code modulation|PCM]] audio with 8-bit [[audio bit depth]] to encode [[analogue signal]]s into a digital stream of 64,000 bit/s. However, in the [[T-carrier]] systems used in the US and Canada, a technique called [[bit-robbing]] uses, in every sixth [[frame (telecommunications)|frame]], the [[least significant bit]] for [[Channel Associated Signaling]] (CAS). This effectively renders the lowest bit of the 8 speech bits unusable for data transmission, and so a 56 kbit/s line uses only 7 of the 8 data bits in each sample period to send data, thus giving a data rate of {{nowrap|8 kHz ×}} {{nowrap|7 bits {{=}}}} {{nowrap|56 kbit/s}}. | The figure of 56 kbit/s is derived from its implementation using the same digital infrastructure used since the 1960s for [[digital telephony]] in the [[public switched telephone network]], which uses a [[sampling rate]] of 8,000 Hz for [[Pulse-code modulation|PCM]] audio with 8-bit [[audio bit depth]] to encode [[analogue signal]]s into a digital stream of 64,000 bit/s.<ref>{{Cite web |last=By |date=2025-03-06 |title=Why 56k Modems Relied On Digital Phone Lines You Didn’t Know We Had |url=https://hackaday.com/2025/03/06/why-56k-modems-relied-on-digital-phone-lines-you-didnt-know-we-had/ |access-date=2025-11-07 |website=Hackaday |language=en-US}}</ref> However, in the [[T-carrier]] systems used in the US and Canada, a technique called [[bit-robbing]] uses, in every sixth [[frame (telecommunications)|frame]], the [[least significant bit]] for [[Channel Associated Signaling]] (CAS). This effectively renders the lowest bit of the 8 speech bits unusable for data transmission, and so a 56 kbit/s line uses only 7 of the 8 data bits in each sample period to send data, thus giving a data rate of {{nowrap|8 kHz ×}} {{nowrap|7 bits {{=}}}} {{nowrap|56 kbit/s}}. | ||
== See also == | == See also == | ||
Latest revision as of 09:36, 7 November 2025
Template:Short descriptionTemplate:More citations needed A 56 kbit/s line is a digital connection capable of carrying 56 kilobits per second (kbit/s), or 56,000 bit/s, the data rate of a classical single channel digital telephone line in North America.[1] Since the wide deployment of faster, cheaper technologies, 56 kbit/s lines are generally considered to be an obsolete technology.[2]
Speed derivation
The figure of 56 kbit/s is derived from its implementation using the same digital infrastructure used since the 1960s for digital telephony in the public switched telephone network, which uses a sampling rate of 8,000 Hz for PCM audio with 8-bit audio bit depth to encode analogue signals into a digital stream of 64,000 bit/s.[3] However, in the T-carrier systems used in the US and Canada, a technique called bit-robbing uses, in every sixth frame, the least significant bit for Channel Associated Signaling (CAS). This effectively renders the lowest bit of the 8 speech bits unusable for data transmission, and so a 56 kbit/s line uses only 7 of the 8 data bits in each sample period to send data, thus giving a data rate of 8 kHz × 7 bits = 56 kbit/s.