Isolated Telephone Interface

Posted on Jun 14, 2012

This circuit allows you to record audio from a telephone line into a tape recorder or computer soundcard. Most of the parts for this circuit can be scrounged from an old modem, with some work, it is possible to rewire the modem circuitry and use the old modem case. Note that some countries have laws that require the user of a phone recording device to notify the party on the other end of the line that they are being recorded.

Click here to download the full size of the above Circuit.

There`s not much to this circuit. The two RJ-11 jacks are set up to feed the telephone circuit through from the wall to the phone. The active signal for a single phone is on the red and green wires. Yellow and black are usually used for a second phon

Visit page

Leave Comment

characters left:

Related Circuits

Busy Telephone line Indicator

Have you ever been using the modem or fax and someone else picks up the phone, breaking the connection? Well, this simple circuit should put an end to that. It signals that the phone is in use by...

Phone line indicator using BF256B

With this circuit can determine whether any of the phones of the same line is busy (it's up the handset), with the help of a LED.To circuit has no measurable effect on the telephone, so that there...

Telephone-controlled tape starter

This circuit converts a tape recorder into a completely automatic telephone conversation recording instrument that needs no external power source. Voltage at the switch terminals of tape recorder...

Telephone status monitor

The LED indicates the status of a remote telephone. The light is off if the phone is hung up. It shines steadily if the phone is off hook, and it flashes on and off while phone rings and for 5...

New Circuits

Zero consumption Anti-theft High power Code Switch for E-Bike Batteries

This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
Ultrasonic distance finder circuit

The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Simple Metal detector circuit with CD4030

Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Fully automatic watering circuit for flower pots

Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
Simple deep searching metal detector circuit

The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
Sub-Harmonic Bass Converter for Electric Guitars

The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
Echo Depth Sounding Sonar for Boats

In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
100W HiFi Audio Amplifier Circuit

This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
Plant-Pot Water Level Indicator Circuit

A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....

Create NOW your QR MENU for your Restaurant / Hotel / Bar / Caffe,

Comprehensive ordering/paying features. fully personalized to suit your Business.

Update Anytime! Easy and Simple!

Popular Circuits

PIC16F84 Solar Charger

The previous version of this device used pulse width modulation (pwm) to control the power from...

Headlight delay unit

This circuit will operate a car"s headlights for a predetermined time to light up the driveway or...

Half-wave rectifier

This circuit provides for accurate half wave rectification of the incoming signal. For positive...

Dc to Dc converter using 555 Timer IC

When the power supply input to IC1 is the output pin 3 at a frequency of 1 kHz. The frequency is...

mosfet Driving LED strip from microcontroller

A strip of LEDs from a microcontroller using PWM to control the brightness. The strip I have...

Final Project circuit

Atmega 8535 Color Conversion to Frequency, the technology of instrumentation that can recognize...

astable circuit produce pulses

This is circuit that first introduced by Signetics Corporation as the SE555/NE555 about 1971. Pin...

Cellphone Charger Using Bike Battery

This is the simple and easy way to tap current from a Motor Bike battery to charge the Mobile...

Smoke Alarm Circuit

The original smoke alarm circuit has some problems and has left some hobbyists and students...

JCM800 2204 bias problem

Alright, my 2204 won`t bias properly. I can`t get the tubes to idle at more than about 14 W (435...