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quantification of the voice in a digital pattern (1s and 0s) using 8 bits
per sample. The result is a 64,000 bits per second (8,000 samples/s
8 bits/sample) stream. This is called DS-0 and is the basis of the
North American Digital Hierarchy. If higher rates of communication
are needed, a multiplexer is used to merge signals together at the
desired rate.

DS-1

The DS-1 signal is created by multiplexing 24 individual DS-0 digi-
tal signals together.Thus, a DS-1 signal is 24 DS-0 signals plus some
extra bits for overhead (that is, 8,000), producing the 1.544-megabit
per second (Mbps) signal. Each DS-0 signal is assigned its own times-
lot on the DS-1. Conceptually, DS-1 is shown in Figure 3-1 (DS-0s).

DS-3

Once the DS-1 is created, 28 DS-1 signals are multiplexed together
to create a DS-3. This higher-speed communications channel com-
bines to create a 44.736-Mbps capacity.Therefore, 672 individual DS-
0 signals can be multiplexed together to create a DS-3. A framing
format is used to carry the DS-1 signals on this high-speed channel,
as shown in Figure 3-2.
DS-3 is an M13 (pronounced M-one-three) asynchronous trans-
mission that uses the M13 Asynchronous Protocol. This means that

Figure 3-1
DS-0 DS-0 DS-0 DS-0
A multiplexing DS-0
overview of DS-1
DS-0 DS-0 DS-0 DS-0 DS-0 DS-0

DS-0 DS-0 DS-0 DS-0 DS-0 DS-0

DS-0