DECADIC or PULSE Dialling

The older method of signalling dialled numbers, where each dialled number is represented by a series of timed breaks (impulse) in the DC current between the telephone and the PSTN equipment. The number of impulses in each impulse string equal the number dialled.

The term DECADIC infers that there are 10 different impulse strings available, one for each of the digits 1 – 0.Special characters like * and # cannot be sent using decadic signalling.