Pulse dialing (IWV) is an older signaling method for telephones, also known as DC signaling. The pulse dialling method is used to transmit the desired call number to the exchange
. In this method, the dial digits on the dial keypad are represented by a corresponding number of direct current pulses, the pulse codes (IKZ). These DC pulses are generated by interrupting the loop current of the exchange battery. The duty cycle of the pulses is 60:40, and the maximum character duration is 10 x 100 ms, or one second. The dial puls
es are transmitted to the telephone exchange where they are used to establish a connection. Thenumber of DC pulses corresponds to
the dialled digit
. Another method that has replaced pulse dialling is multifrequency dialling (DTMF).