Telephone and intercom related schematics

  • Telephone recording circuit
  • Infinity Transmitter Schematic and Plans
  • Digisound ring modulator
  • Incoming call indicator
  • Telephone Ring Generator Using 60Hz Power Transformer
  • Telephone Ring Generator Using Switching Power Supply
  • Telephone In-Use LED Indicator
  • Telephone In-Use Relay Circuit
  • Telephone Audio Interface
  • Telephone interfacing / caller ID using a PIC microcontroller
  • Home made PBX / PABX
  • Ringing Phone Light Flasher
  • Phone Busy Indicator
  • FM Telephone Bug
  • Cut Phone Line Detector
  • Simple Phone Tap
  • Telephone Hold Button
  • Telephone Recorder
  • 300 baud modem circuit schematic
  • Telephone music on hold box
  • Telephone ring controlled relay
  • 1-line telephone status indicator (PDF)
  • Line in use indicator (PDF)
  • 4-line telephone status indicator (PDF)
  • Caller ID decoder
  • Telephone in use light
  • Detecting a telephone RING
  • Phone In-Use Light
  • Phone to audio interface
  • Phone Off-Hook Indicator
  • 'phone rang' indicator light
  • Phone Line to Audio
  • Phone in-use
  • Telephone Line Monitor
  • Use old phones as an intercom
  • Phone-In-Use indicator
  • Hold function for Telephone
  • Digital/Standard Phone Line Tester
  • Caller ID decoder part 1
  • Caller ID decoder part 2
  • DTMF decoder / logger
  • Cellular Phone calling Detector
  • Phone line in use indicator
  • Telephone music on hold interface
  • Soft musical telephone ringer
  • Telephone amplifier
  • Telephone line monitor
  • Cut telephone line detector
  • FM telephone line bug transmitter
  • Simple telephone line tap for intercepting telephone calls
  • The Link A2B+1 (the Link Telephone Intercom - DTMF version)
  • The Link 4+0 - Internal Intercom
  • The Original 2 Phone Intercom Link Design
  • 8-line intercom system using 89C51 microcontroller
  • Universal telephone hold
  • Talking phone dial monitor
  • Telephone line simulator
  • Telephone privacy adapter
  • Telephone ringing circuits
  • Simple circuit to connect telephone equipment to audio mixer
  • NCDS Interface Schematic for Nokia 3110, 8110, 8110i
  • Assorted telephone circuits
  • Greek telecard reader
  • Phone ring circuit schematic
  • Cut phone line detector
  • Telephone autodialler
  • Taxi phone automatic dialler