Telephone instrument with flash key - has cct for delivery of brief interruption of specified duration

摘要

The flash key produces a time defined switching state change with duration independent upon duration of key operation. This takes place during a state existing when the cradle switch is not operated. The above flash key is also used for carrying out a function depending on the cradle switch rest state. This additional function is carried out by a switch mechanically coupled with the flash key, or by an electronic switch controlled by the flash key and consisting of two transistors activated by the flash contact opening. Its activation is blocked by a diode when the cradle switch is operated.