Local call-timing cct. for telephone exchange - has control line connecting to call-timing-pulse counter

摘要

The local call-timing circuit, for telephone exchanges, has a control line passing through an additional unit and switched to connect with the counter that counts the call-timing pulses. The control line ahs a capacitor coupled to it such that the counter is set at the beginning of a conversation when the constant count-voltage is applied to the appropriate connecting line. When the called subscriber replaces his hand-set, signals to this effect pass to a detector in the additional unit which then initiates the control line's disconnection. The installation does not require any far ranging modification of existing equipment.