Schematics > Telephone related > Cut Phone Line Detector
Cut Phone Line DetectorA while ago I got an email asking for the schematic of a circuit to detect
cut phone lines. It didn't take me long to find this circuit in
Electronics Now. When the circuit
detects that a phone line has been cut, it activates a MOSFET which can be used
to drive a relay, motor, etc. It can also be connected to a security system.
Schematic
Parts
| Part |
Total Qty. |
Description |
Substitutions |
| R1, R2, R3 |
3 |
22 Meg 1/4 W Resistor |
|
| R4 |
1 |
2.2 Meg 1/4 W Resistor |
|
| C1 |
1 |
0.47uF 250V Mylar Capicitor |
|
| Q1 |
1 |
2N3904 Transistor |
2N2222 |
| Q2 |
1 |
2N3906 Transistor |
|
| Q3 |
1 |
IRF510 Power MOSFET |
|
| D1 |
1 |
1N914 Diode |
|
| Load |
1 |
See "Notes" |
|
| MISC |
1 |
Wire, Phone Connectors, Circiut Board |
|
Notes
1. The "Load" can be a relay, lamp, motor, etc. The circuit can also be
connected to a security system to sound an alarm in case the phone line is cut.
2. If the circuit is connected to a security system or other circuit, both
circuits must be electrically isolated from each other using an opto-isolator,
relay, etc. This also means that the Cut Phone Line Detector must be powered by
a seperate 9V supply.
Title: Cut Phone Line Detector
Source: www.aaroncake.net/circuits/
Published on: 2005-02-10
Reads: 281
Print version:  Other schematics from Telephone related
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