關鍵字：電話斷線探測器（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，我收到一封電子郵件，詢問電路原理圖，以檢測切斷的電話線。 在電子產品現在找到這個電路并沒有花太多時間。 當電路檢測到電話線被切斷時，它會激活一個可用于驅動繼電器，電機等的MOSFET。它還可以連接到安全系統。

Circuit diagram 電路原理圖

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.“負載”可以是繼電器，燈，電動機等。電路也可以連接到安全系統，以便在電話線被切斷時發出警報。
2.如果電路連接到安全系統或其他電路，則兩個電路必須使用光隔離器，繼電器等彼此電隔離。這也意味著切割電話線路檢測器必須由單獨的9V供電 供應。