Telephone call unit with single push button - has cursor moving along contact track to control output signals

摘要

Two telephone lines (L1, L2) from a subscriber are connected to the network by closure of two contacts (C1, C2) when the handset is lifted. Calling pulses are generated in a pulse generator circuit (12) operating a relay (11) contact (10), and deriving its power requirements from the telephone lines through a rectifier and stabiliser circuit (17). A telephone number is generated by earthing pusle generator inputs (E1, to E0) in the correct order by a cursor (22) which is pushed along a track (23) by a spring loaded button (15).