关键字：电话断线探测器（英文呢）

A 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.

不久之前，我收到一封电子邮件，询问电路原理图，以检测切断的电话线。 在电子产品现在找到这个电路并没有花太多时间。 当电路检测到电话线被切断时，它会激活一个可用于驱动继电器，电机等的MOSFET。它还可以连接到安全系统。

Circuit diagram 电路原理图

Parts
R1, R2, R3 22 Meg 1/4 W Resistor
R4 2.2 Meg 1/4 W Resistor
C1 0.47uF 250V Mylar Capicitor
Q1 2N3904 Transistor or 2N2222
Q2 2N3906 Transistor
Q3 IRF510 Power MOSFET
D1 1N914 Diode
Load See "Notes"
MISC 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.

1.“负载”可以是继电器，灯，电动机等。电路也可以连接到安全系统，以便在电话线被切断时发出警报。
2.如果电路连接到安全系统或其他电路，则两个电路必须使用光隔离器，继电器等彼此电隔离。这也意味着切割电话线路检测器必须由单独的9V供电 供应。