| 摘要 |
<p>In key telephone systems where a plurality of stations have access to a line by merely depressing a line key, a circuit is provided to prevent that station from entering a busy line. The circuit uses a single relay per station to provide a normal condition of privacy for any line at a station to equipped. The circuit senses the condition of the line and on a busy condition, the station cannot access the busy line. By providing all stations of a key group with privacy circuits, all stations can have complete privacy on line calls. Privacy control is possible on less than all stations of a system and less than all lines by selective deployment of privacy circuits. Optionally, a privacy release button can be provided to allow a station to enable other stations to access that busy line. Protection has been built into the circuit against transient surges and the like.</p> |
