Combined timer and lock for telephone - has key in sliding cylinder connected to cam operated spring contact to control speech time

摘要

The telephone key switch comprises a normally withdrawable key (S) a sliding cylinder (Z) a locking cylinder (Sp) and a cammind disc (N) with an extended portion which is operative for a secotr of the disc periphery during which it is operative to close the points of a pair of leaf spring contacts (K). In the neutral position the key si withdrawable and the contacts open. Whe speech is desired the key is pushed in and the locking cylinder rotates for a prescribed period. During the remainder of the cycle the key is held and may not be withdrawn until the counter is reset presumably aftr payment of a specified tariff.