Pulse dialing
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Pulse dialing is a signaling technology in telecommunications in which the direct current flowing in the telephone local loop circuit is interrupted in a pattern according to a coding system for each
The model 500 rotary dial telephone by Western Electric was a pulse-dialing instrument.
British (GPO) Type 232 telephone of 1932
Swedish phone with one pulse for 0
DTMF signaling
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Dual-tone multi-frequency signaling is a telecommunication signaling system using the voice-frequency band over telephone lines between telephone equipment and other communications devices and switchi
Pulse dialing
…of using mechanical reed relays was too unreliable until transistors transformed the industry. In 1963, the Bell System introduced to the public dual-tone multi-frequency (DTMF) technology under the name Touch-Tone, which was a trademark in the U.S. until 1984. The Touch-Tone system used push-button telephones. In the…
The Western Electric 2500, a typical late 20th century American touch-tone telephone
Autovon keypads were a typical application for use of all sixteen DTMF signals. The red keys in the fourth column produce the A, B, C, and D DTMF events.
Two CMD CM8870CSI DTMF receivers