5 Useful Telephone System Circuits

This page features the circuit diagrams and information for the following circuits:

Telephone Ring Generator Using Switching Supply

This circuit will ring at telephone at defined intervals - as set by the timing components of the circuit

Telephone Ring Generator Using Small Power Transformer

This circuit will also ring at telephone at defined intervals

Telephone In-Use Indicator

Circuit checks the telephone line to determine whether or not it is in use. Lights an LED (Light Emitting Diode).

Telephone In-Use Relay Controller

Same as previous, however it uses a relay so that you can do more than just light an LED.

Telephone Audio Interface

Allows for the extraction of audio from a telephone line