Telephone subscriber circuit with three point dialling device - having electronic pulse generator to drive transistor forming pulsing contacts

摘要

The telephone subscriber circuit is designed not only to accommodate normal dialling devices but also those that employ abbreviated or shortened numbers for dialling subscribers who are, e.g. frequently wanted, and that permit repeated dialling at the press of a button. The circuit contains a dialling device with only three connection points. A transistor forms the pulsing contacts driven by the device's electronic pulse generator. This transistor (T1) is shunted out and its base circuit open-circuited while a conversation is taking place. The shunting-out is accomplished by contacts (nsa2). The transistor is controlled via a log circuit.