AT&T 7100 series Multiplexed Communication, Types of Multiplexing, Time-Division Multiplexing

MULTIPLEXED COMMUNICATION

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As signals are transmitted away from the switch and onto a public or private network, multiplexed communication becomes an option. Multiplexed communication results from the interleaving of signals from multiple circuits into a single communications path. For transmissions with the same destination, it is an economic alternative to using multiple single-trunk transmission paths.

TYPES OF MULTIPLEXING

Three types of multiplexing are used in switch communications: frequency-division multiplexing, time- division multiplexing, and statistical multiplexing.

Frequency-Division Multiplexing

Frequency-division multiplexing provides a number of simultaneous channels over single analog medium (twisted pair, coax, microwave, and so on) by using a different frequency band for the transmission of each channel. Each channel provides a discrete data or conversation path.

Frequency-division multiplexing is used only for public network transmission facilities. The analog trunk groups attached to private communication system switches — like the System 75, System 85, and DEFINITY Generic 1 and Generic 2 communications systems — are not multiplexed.

Time-Division Multiplexing

In time-division multiplexing, a single transmission path is divided into several different communications channels. The channels are assigned in units called time slots.

YOUR TIME SLOT

MY TIME SLOT

125 μSECONDS 125 μSECONDS

Figure 1-4. Time Slot

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