cut Phone Line Detector schematic | Electronic Schematic Diagram https://electronicscheme.net Schematic Diagram & PCB Design Tue, 20 Jan 2015 13:25:41 +0000 en-US hourly 1 https://i0.wp.com/electronicscheme.net/wp-content/uploads/2017/05/cropped-transparent_text_effect.png?fit=32%2C32&ssl=1 cut Phone Line Detector schematic | Electronic Schematic Diagram https://electronicscheme.net 32 32 129969089 Cut Phone Line Detector https://electronicscheme.net/cut-phone-line-detector/?utm_source=rss&utm_medium=rss&utm_campaign=cut-phone-line-detector https://electronicscheme.net/cut-phone-line-detector/#comments Sun, 15 May 2011 16:18:14 +0000 http://electronicscheme.net/?p=945 This cut phone line detector circuit is used to detect whether your phone line is active or not. Components List: R1,R2,R3 = 22M Ohms R4 […]

The post Cut Phone Line Detector first appeared on Electronic Schematic Diagram.]]> This cut phone line detector circuit is used to detect whether your phone line is active or not.

Cut Phone Line Detector

Components List:
R1,R2,R3 = 22M Ohms
R4 = 2.2M Ohms
C1 = 0.47uF/250V Mylar caps
D1 = 1N914, NTE519, or other small signal diode
Q1 = 2N3904, NTE123AP
Q2 = 2N3906, NTE159
Q3 = IRF510, NTE2382,? MosFet

This kind of circuit speaks for itself. While the phone line is okay, Q1 works as a short that has a extremely high resistance/ohms value via R1, R2, and R3 for a total close to 66 MegaOhm, so it is very high. When the phone line is cut (open), it triggers the MosFet (Q3) via transistor Q2 to drive the load. Replacements are acceptable, not one of the parts are crucial.

The ‘LOAD’ can be anything you like. A lamp, relay, motor, tape-recorder, stereo, security system, or anything else.

Remember that telephone providers do not like to have anything ‘directly’ connected to their wire connections for apparent reasons, so work with this circuit at your own risk. If you want to experiment with it safely, work with an Opto-Isolator or something…

Circuit designed by Tony van Roon

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