Inchannel Signalling

For data transfer and path setup for conversation, various forms if signalling were developed in automatic switching system. Various classifications are mentioned in last section. In this section, the inchannel signalling which uses same path for control signals and data/speech transfer are discussed.

7.3.1. Loop Disconnect - dc Signalling

The earliest and still the most common telephone set is the rotary dial telephone. The mechanism to transmit the identify of the called subscriber to exchange is pulse dialling. The basic idea is to interrupt the d.c. path of the subscriber's loop for a specified number of short periods to indicate the number dialled. This is called loop-disconnect (or rotary) signalling. Fig. 7.2. shows the finger plate arrangement of rotary dial telephone and a typical pulse pattern.

Dial holes

Finger stop

(a) Finger plate arrangement

Dial holes

Finger stop

(a) Finger plate arrangement

Digit 3

Digit 4

1 pulse

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