Cut Phone Line Detector
The circuit designed for detecting cut phone lines utilizes a simple yet effective configuration that leverages a MOSFET as the primary switching element. The schematic typically consists of a few key components: a voltage divider, a comparator circuit, a MOSFET, and a load, which may include a relay, lamp, or motor.
When the phone line is intact, the circuit operates normally, allowing a small current to flow through the voltage divider, which keeps the gate of the MOSFET in a low state. This prevents the MOSFET from conducting, and consequently, the load remains off. Upon detecting a cut in the phone line, the voltage at the input to the comparator changes significantly, triggering the MOSFET to turn on. This activation allows current to flow through the load, which can be a relay that closes a circuit to sound an alarm or activate another device.
The load can be connected to various devices, including alarms or indicators, which will alert users of the phone line disruption. Additionally, if integrated into a broader security system, the output from the MOSFET can be used to trigger additional security measures, ensuring comprehensive monitoring and response capabilities.
It is crucial to ensure that the circuit is designed with appropriate ratings for the MOSFET and load components to handle the expected current and voltage levels. Furthermore, if the circuit is connected to a security system, the integration must be carefully planned to avoid interference and ensure reliable operation. This involves proper isolation and signal conditioning to maintain the integrity of both systems.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. 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 b 🔗 External reference
Related Circuits
This circuit is capable of detecting smoke and various gases, including carbon monoxide (CO), carbon dioxide (CO2), methane, and coal gas, with a sensitivity of 10 parts per million (ppm). It employs a heated surface semiconductor sensor, which detects...
The schematic consists of three main components. The first component is the sensor circuitry, which connects the accelerometer to the analog-to-digital converters (A/D converters). The second component is the power circuit, featuring an On/Off switch, a 3.7V battery, and...
20W bus radio and megaphone circuit utilizing the TDA2005S double low-frequency power amplifier integrated circuit design. The front end can be connected to either a microphone input or a low-frequency radio output voltage amplification stage. Each TDA2005S provides 10W...
Charging a mobile phone or cellphone battery presents a significant challenge while traveling, as a power supply source is often not readily available. If the cellphone remains switched on continuously, its battery can deplete within five to six hours,...
Drawing transistors that comprise the gate VTi, VT2, VT3, and similar components. The schematic involves a configuration of transistors designated as VTi, VT2, and VT3, which are integral to forming a gate structure. These transistors are typically arranged in a...
The telephone-line decibel meter and line-voltage sensor enables accurate monitoring and adjustment of telephone sound levels. The 600-ohm resistor appropriately terminates the line. The power consumption from the 9-volt battery is 2 mA, and the meter offers a ±30...