Phone Circuits
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Here is a very simple telephone broadcaster transmitter which can be used to eavesdrop on a telephone conversation. The circuit can also be used as a wireless telephone amplifier. One important feature of this phone transmitter is that the circuit derives.... -
This is a very small telephone exchange attached only two ordinary Tele phones. Fully bi-directional facility with an intercom system. When a phone is in off hook condition, Exchange will detect it & send ringing pulse to other phone. When it will be picked.... -
In the process of adapting an old phone to be used as an Bluetooth phone. I am currently testing the ringer circuit, which I build using the schematics provided by Sparkfun. Now, when I hook up just the right part of the schematic to a 3. 5V source (Vcc), I.... -
What kind of microphone or mouthpiece I can use to connect across a pots telephone line in order to send dtmf tones ( no voice ) dtmf only. Can I use a regular mic or does it have to be a certain type, I am using a 300 ohm resistor to hold open the line.... -
With the aid of an (old) moving coil instrument it is very little effort to make a simple voltmeter that, at a glance, indicates the status of a telephone line. Because the input impedance of this circuit is very high, there is no problem in having it.... -
Controlling devices using switches are common. From a few decades controlling devices using remote control switches like infrared remote control switch, wireless remote control switches, light activated switches are becoming popular. But these technologies.... -
The transformer is a 600:600 ohms transformer (also named 1:1 ratio 600 ohm transformer) : more or less the same number of turns on both primary and secondary coils, and optimized to work at 600 ohms load. Selectronic sells one here. I measured the primary.... -
In this file is a schematic for a simple wiretap & instructions for hooking up a small tape recorder control relay to the phone line. First, I will discuss taps a little. There are many different types of taps. There are transmitters, wired taps, and.... -
Just hook this Alarm Phone Dialer up to something you would like to monitor, for example, a high water alarm, low temperature alarm, back window, garage door, etc. When the system is activated it will call a number of programmed numbers to let you know the.... -
Depending on local regulations and the telephone company you happen to be connected to, the voltage on a free telephone line can be anything between 42 and 60 volts. As it happens, that`s sufficient to make a diac conduct and act like a kind of zener diode.... -
The circuit presented here can be used for connecting two telephones in parallel and also as a 2-line intercom. Usually a single telephone is connected to a telephone line. If another telephone is required at some distance, a parallel line is taken for.... -
Normally the base of a cordless phone has an adaptor and the handset has Ni-Cd cells for its operation. The base unit becomes in-operative in case of power failure. Under such conditions, it is better to provide a backup using Ni-Cd cells externally. Here is.... -
Using modulated rectangular waves of different time periods, the circuit presented here produces ringing tones similar to those produced by a telephone. The circuit requires four astable multivibrators for its working. Therefore two 556 ICs are used here..... -
Electronic FM Telephone Transmitter SchematicThe following schematics design pictures is a circuit diagram FM telephone transmitter that built on a PC board layout which is so small it can simply be fitted within the housing of a telephone creating it an.... -
Telephones are reaching its death point all over the world. however there is more than 350 million mobile phone users in india, but there are tremendous number of telephone users are there also. Well, this telephone timer is designed to help saving by.... -
This assemblage was advised for amateurs owning an old accumulating of vinyl recordings and absent to accept it digitally remastered into a claimed computer. Or sometimes they would accept to an old, invaluable, LP accumulating through their avant-garde.... -
.png "Mobile cell phone detector (sniffer) circuit diagram: engineering and diploma project")
Here is a simple engineering project circuit of handy mobile cell phone detector (sniffer). This pocket-sizedmobile communication detector or sniffer can sense the existence of a mobile device. So it can be used to avoid the use of mobile phones in private.... -
The contact less telephone ringer circuit can produce a ring as well as a visual indication when a call comes. The main advantage is that since there is no direct contact between the phone line and the circuit there is no chance for a loading or disturbance.... -
A simple telephone transmitter circuit that is ideal for transmitting the telephone conversation through small distances. The circuit is very simple and uses only few components. The entire circuit can be easily included in the telephone itself or in the.... -
Here is a simple head phone amplifier circuit that can be used to drive your head phone if your music player doesn`t have enough power to drive your head phones. The circuit is straight forward and uses only three transistors. The transistor Q1 (BC 239) and.... -
When the telephone rings the line voltage rises to 72 volts. At this time the LED in the opto-coupler glows and the transistor conducts. Due to this the transistor Q1 conducts. This makes the relay ON. The load connected to the relay whether bulb or bell.... -
Here is a simple circuit that can be used as a telephone status indicator. When the telephone is in use (off hook) the transistor Q1 switches ON making the red LED D2 glow. When the telephone is not in use (on hook) the Q1 turns OFF and Q2 turns ON. This.... -
The circuit depicted here can be used as an indicator when the telephone receiver is off-hook. The circuit can be in corporated with old telephones that does not have such an indicator. The circuit uses a complementary darling to pair using Q1 (2N3904)and Q2.... -
The circuit given below is of a telephone operated DTMF remote. The circuit can be used to switch up to 9 devices using the keys 0 to 9 of the telephone. Digit 0 is used to switch the telephone system between remote switching mode and normal conversation.... -
Here is a simple circuit based on IC uA 741 that can be used to pickup voice from telephone lines without even contacting the line. If a high impedance magnetic core is placed near a telephone instrument or near one of the telephone wires, it picks up.... -
This is a simple, but very useful circuit that can be used to transmit telephone conversations. When the telephone receiver is on hook the voltage across the lines will be about 48 volts. The preset R7 is so adjusted to obtain a 24. 7 V across between the.... -
This circuit bellow shows a teleremote circuit which enables switching ‘on and ‘off of appliances through telephone lines. Can be used .... -
The following circuit shows about A933 Transistor Telephone Listening Circuit Diagram. Features: can be tuned from 88 to about 94Mhz, simple .... -
This circuit shows about Remote Control Using Radio Telephone Circuit Diagram. Features: used to switch appliances from any distance, overcoming .... -
The AAT1265 evaluation board provides a platform for the testing and evaluation of the AAT1265 low voltage 2MHz Step-up Regulator The evaluation board demonstrates suggested size and placement of external components to main- tain output voltage regulation.... -
The AN7158N is an integrated circuit designed for power Amplifier of 7. 5W (16V, 4) output with low noise and low distortion, and it suits TV set with multi-sound. Stereo operation is enabled due to incorporating two Amplifiers on one chip. 12-pin SIL....
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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.... -
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.... -
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.... -
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.... -
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.... -
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,.... -
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.... -
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.... -
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.....
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