Telephone listen in equipment - has bridge connections and switches allowing combinations of listen and speak

摘要

The telephone liste-in equipment has a listen-in transformer connected to a line by switches used for other purposes. The listen-in/speak equipment can be used for different types of operation, e.g. speak from listen position, preferred listen positionS, and listen suppression for speak positions. Bridge points per speak position and line are present whose connection determines the right to listen. Switches allow only one listen position to listen on one line. Further bridge point connections determine speaking during listening.