Key Pulser

a push-button number selector installed as part of subscribers’ telephone sets, telephone switchboards, control and test devices, and other equipment. A key pulser usually has ten principal push buttons, each marked with a decimal numeral, and several additional push buttons, which may be marked with letters. Depressing a push button briefly causes an appropriate signal to be sent to a receiving device, for example, an automatic telephone exchange, which accepts the selected numeral. Thus, the sequential pushing of seven buttons can transmit to an automatic telephone exchange the seven-digit number of the subscriber being called. Seven to eight numerals can be selected per second’on a key pulser—a rate approximately ten times faster than is possible with a disk-type telephone dial.

Depending on the arrangement of push buttons, key pulsers are designated as one-, two-, three-, and four-row units. Three-row units are used principally in telephones and switchboard equipment. Telephone key pulsers are so designed that they can replace disk dials. Key pulsers for switchboards usually have two additional push buttons for service use, for example, to signal the end of a number selection or to select an individual switchboard operator’s station.