As pulse dialing came into use for telephone exchanges, pen registers had obvious applications as diagnostic instruments for recording sequences of telephone dial pulses.

In the decades following, pulse dialing was gradually phased out as the primary signaling method to the central office, but many systems still support rotary telephones for backward compatibility.

Pulse dialing is a signaling technology in telecommunications in which a direct current local loop circuit is interrupted according to a defined coding system for each signal transmitted, usually a digit.

As pulse dialing is achieved by interruption of the local loop, it was in principle possible to dial a telephone number by rapidly depressing the switch hook the corresponding number of times for each digit at approximately ten taps per second.