Editing Digital Signal 0 (section)

{{Refimprove|date=November 2007}}
'''Digital Signal 0''' ('''DS0''') is a basic digital signaling rate of 64 kilobits per second ([[kbit/s]]), corresponding to the capacity of one analog [[voice-frequency]]-equivalent [[communication channel]].<ref>{{Cite web |url=http://www.its.bldrdoc.gov/fs-1037/dir-012/_1658.htm |title=Definition from Federal Standard 1037C |access-date=2008-10-01 |archive-url=https://web.archive.org/web/20110927004401/http://www.its.bldrdoc.gov/fs-1037/dir-012/_1658.htm |archive-date=2011-09-27 |url-status=dead }}</ref> The DS0 rate, and its equivalents E0 in the [[E-carrier]] system and T0 in the [[T-carrier]] system, form the basis for the [[Digital multiplex hierarchy|digital multiplex transmission hierarchy]] in telecommunications systems used in North America, Europe, Japan, and the rest of the world, for both the early [[plesiochronous]] systems such as [[T-carrier]] and for modern synchronous systems such as [[Synchronous Digital Hierarchy|SDH]]/[[SONET]].

The DS0 rate was introduced to carry a single digitized voice call. For a typical phone call, the audio sound is digitized at an 8 [[kHz]] sample rate, or 8000 samples per second, using 8-bit [[pulse-code modulation]] for each of the samples. This results in a data rate of 64 [[kbit/s]].

Because of its fundamental role in carrying a single phone call, the DS0 rate forms the basis for the digital multiplex [[transmission (telecommunications)|transmission]] hierarchy in telecommunications systems used in North America. To limit the number of wires required between two involved in exchanging voice calls, a system was built in which multiple DS0s are [[multiplexed]] together on higher capacity circuits. In this system, twenty-four (24) DS0s are multiplexed into a  [[Digital Signal 1|DS1]] signal. Twenty-eight (28) DS1s are multiplexed into a [[Digital Signal 3|DS3]]. When carried over copper wire, this is the well-known [[T-carrier]] system, with [[Digital Signal 1|T1]] and [[Digital Signal 3|T3]] corresponding to DS1 and DS3, respectively.  

Besides its use for voice communications, the DS0 rate may support twenty 2.4&nbsp;kbit/s channels, ten 4.8&nbsp;kbit/s channels, five 9.67&nbsp;kbit/s channels, one 56&nbsp;kbit/s channel, or one 64&nbsp;kbit/s clear channel.

E0 (standardized as [[G.703|ITU G.703]]) is the European equivalent of the North American DS0 for carrying  a single voice call. However, there are some subtle differences in implementation. Voice signals are encoded for carriage over E0 according to [[G.711|ITU G.711]]. Note that when a T-carrier system is used as in North America, [[robbed bit signaling]] can mean that a DS0 channel carried over that system is not an error-free bit-stream. The [[out-of-band signaling]] used in the European E-carrier system avoids this.