Pushbutton keyboard telephone receiver - has security lock connected to knife contacts on printed circuit board

摘要

The telephone terminal has its pushbutton keyboard connected via a four-wire cable to the plug that plugs onto knife contacts on the pc board. The security lock is connected directly to tags projecting from the same knife contacts. The security lock (2) is not only connected to the board's contacts but also via a separate knife contact (14) to a wire (10) coming directly from the keyboard (1). This knife contact can also be connected into a socket in the plug already occupied by one of the board's knife contacts.