Digital Signal 0

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Digital Signal 0 (DS0) is a basic digital signaling rate of 64 kbit/s, corresponding to the capacity of one voice-frequency-equivalent channel.

The DS0 rate forms the basis for the digital multiplex transmission hierarchy in both the European and North American systems, for both the early plesiochronous systems such as T-carrier, and for modern synchronous systems such as SDH/SONET.

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.

To carry a typical phone call, the audio sound is digitized at an 8 kHz sample rate using 8-bit pulse-code modulation. Multiple DS0s are multiplexed together on higher capacity circuits. Twenty-four (24) DS0s make a DS1 signal. When carried over copper wire, this is the well-known T-carrier system, T1 (the European equivalent is an E1, containing thirty-two 64 kbit/s channels).

Note that when a T-carrier system is used, 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 system avoids this.

E0 (G.703) is related to DS0; audio data is sent over E0 according to G.711.