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Line monitor circuit diagrams

Phone Busy Indicator
Phone Busy Indicator
December 2, 2010

Have you ever been using the modem or fax and someone else picks up the phone, breaking the connection? Well, this simple circuit should put an end to that. It signals that the phone is... [more]

Telephone line monitor
Telephone line monitor
October 25, 2010

This nifty little circuit lets you record your phone conversations automatically. The device connects to the phone line, your tape recorder's microphone input, and the recorder's remote control jack. It senses the voltage in the... [more]

Telephone line monitor
Telephone line monitor
October 14, 2010

If you feel that somebody is tampering with your telephone line you might find this little circuit useful. It detects if there is another telephone connected to the line, if there is a short or... [more]

Cut Phone Line Detector
Cut Phone Line Detector
June 22, 2010

Cut Phone Line Detector [more]

Telephone In-Use Relay Controller
Telephone In-Use Relay Controller
April 28, 2010

Telephone In-Use Relay Controller [more]

Telephone In-Use Indicator
Telephone In-Use Indicator
April 28, 2010

Telephone In-Use Indicator [more]

Telephone Line Ring and Indicator
Telephone Line Ring and Indicator
April 25, 2010

It is a relatively simple circuit, with which we can have optical and sound clue, when we have telephone ring in the line of telephone. The calls in the line, are changed in pulses of... [more]

Clue engaged telephone line
Clue engaged telephone line
April 25, 2010

If we have a lot of parallel telephones on a telephone line, we needed a unit that will have the possibility of showing if somebody of the telephone has raised the earphone. [more]

Telephone Line Monitor
Telephone Line Monitor
April 25, 2010

A very simple circuit, that will find application in the case where you have a lot of telephones installed on a telephone line and would want to know if somebody of them is open. Thus... [more]