Telephone-related ASCII Schematics V1.01
   Telephone in use light
   Detecting a telephone RING
   (manual) Phone In-Use Light
   Phone to audio interface (SSI202 input)
   Phone Off-Hook Indicator
   'phone rang' indicator light
   Phone Line to Audio
   Phone in-use
   Telephone Line Monitor (Plans)
   Use old phones as an intercom
   Phone-In-Use indicator
   Telephone Power?
   Hold function for Telephone
   Digital/Standard Phone Line Tester