Digital Signal 0 (DS0) is a basic digital signaling rate of 64 kilobits per second (

kbit/s In telecommunications, data-transfer rate is the average number of bits (bitrate), characters or symbols ( baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are mult ...

), corresponding to the capacity of one analog

voice-frequency A voice frequency (VF) or voice band is the range of audio frequencies used for the transmission of speech. Frequency band In telephony, the usable voice frequency band ranges from approximately 300 to 3400 Hz. It is for this reason that ...

-equivalent

communication channel A communication channel refers either to a physical transmission medium such as a wire, or to a logical connection over a multiplexed medium such as a radio channel in telecommunications and computer networking. A channel is used for informa ...

. The DS0 rate, and its equivalents E0 in the

E-carrier The E-carrier is a member of the series of carrier systems developed for digital transmission of many simultaneous telephone calls by time-division multiplexing. The European Conference of Postal and Telecommunications Administrations (CEPT) orig ...

system and T0 in the

T-carrier The T-carrier is a member of the series of carrier systems developed by AT&T Bell Laboratories for digital transmission of multiplexed telephone calls. The first version, the Transmission System 1 (T1), was introduced in 1962 in the Bell Syste ...

system, form the basis for the digital multiplex

transmission Transmission may refer to: Medicine, science and technology * Power transmission ** Electric power transmission ** Propulsion transmission, technology allowing controlled application of power *** Automatic transmission *** Manual transmission ** ...

hierarchy in telecommunications systems used in North America, Europe, Japan, and the rest of the world, for both the early

plesiochronous In telecommunications, a plesiochronous system is one where different parts of the system are almost, but not quite, perfectly synchronised. According to ITU-T standards, a pair of signals are plesiochronous if their significant instants occur at ...

systems such as

and for modern synchronous systems such as

SDH SDH may refer to: Science, medicine and technology * Serine dehydratase, an enzyme * L-sorbose 1-dehydrogenase, an enzyme * Succinate dehydrogenase, an enzyme * Shubnikov–de Haas effect * Social Determinants of Health, economic and social condit ...

SONET Synchronous optical networking (SONET) and synchronous digital hierarchy (SDH) are standardized protocols that transfer multiple digital bit streams synchronously over optical fiber using lasers or highly coherent light from light-emitting diode ...

. 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 The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...

sample rate, or 8000 samples per second, using 8-bit

pulse-code modulation Pulse-code modulation (PCM) is a method used to digitally represent sampled analog signals. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio applications. In a PCM stream, the a ...

for each of the samples. This results in a data rate of 64

. Because of its fundamental role in carrying a single phone call, the DS0 rate forms the basis for the digital multiplex

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 In telecommunications and computer networking, multiplexing (sometimes contracted to muxing) is a method by which multiple analog or digital signals are combined into one signal over a shared medium. The aim is to share a scarce resource - a ...

together on higher capacity circuits. In this system, twenty-four (24) DS0s are multiplexed into a DS1 signal. Twenty-eight (28) DS1s are multiplexed into a DS3. When carried over copper wire, this is the well-known

system, with T1 and T3 corresponding to DS1 and DS3, respectively. Besides its use for voice communications, the DS0 rate may support twenty 2.4 kbit/s channels, ten 4.8 kbit/s channels, five 9.67 kbit/s channels, one 56 kbit/s channel, or one 64 kbit/s clear channel. E0 (standardized as 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 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 In telecommunication, signaling is the use of signals for controlling communications. This may constitute an information exchange concerning the establishment and control of a telecommunication circuit and the management of the network. Classi ...

used in the European E-carrier system avoids this.

References

See also