Phone Circuits
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This circuit is used to record telephone conversations on your landline telephone. All you will need is this small circuit and subscription of your PC. There are few times when we forget what we said or told us. So we need recording. Sometime, not many years.... -
The circuit can be used in telephone lines for speech activity detection purposes. This detection is very useful in the case of half-duplex conversation between two stations, in the case of simultaneous transmission of voice and data over the same pair of.... -
Two integrated tone decoders, XR-567 units, can be connected (as shown in Fig. 1A) to permit decoding of simultaneous or sequential tones. Both units must be on before an output is given. R1C1 and R'IC'l are chosen, respectively, for Tones 1 and 2. If.... -
The on-hook (no load) voltage across the red-green wires will be 48 V or slightly less when all telephones are on-hook (disconnected). When any telephone goes off-hook the load current flowing in the telephone causes the voltage to fall below 5 volts dc..... -
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 applied to a pair of Darlington-connected transistors, Ql and.... -
Transistor Ql of the headset amplifier circuit amplifies the 30 mV signal, that would have gone to the earphones, to .5 V. which sufficiently drives the stereo earphones. Capacitor Cl blocks any de current from shorting back into the telephone base..... -
This circuit shows the TP5700 directly interfacing to a low-voltage DTMF generator. VREGt supplies the necessary 2-V minimum bias to enable the TP5380 to sense key closures and pull its mute output high. VREGt then switches to a 3-V regulated output to.... -
This circuit consists of two audio channels, a control circuit, and a hybrid irlterface circuit. The gain of each audio channel is con· trolled by the control circuitry, with the use of a voltage controlled amplifier (VCA). The inputs to the control.... -
Here is a simple method of series connection into the telephone set suitable for PABX or short line applications. When the telephone handset is lifted, Cl is charged via D1 to (Vz1 -0.7) V and DF320 power on reset occurs. When the first keyed digit is.... -
The oscillator is a Motorola MC14410CP chip using a 1-MHz crystal. The chip generates both the high and low tones, feeding the energy to the amplifier through 1-K resistors and the 1-I"F capacitor. Values for the output resistors can vary from a few.... -
The TP5700 or TP5710 can reduce the number of components required to build a pulse-dialing telephone, as shown. The usual current source can be eliminated by using the VREGl output to power a TP50982A low-voltage (1. 7 V) pulse dialer via a blocking diode..... -
When the handset is lifted and power is applied to the circuit, Q2 is fed base current through R2, which in turn drives Ql. C2 is charged via R3 in series with D1 to (Vz1 -0. 7) V. When the minimum operating Vnv voltage is reached, power on reset occurs.... -
A sensitive-gate SCR provides a line-holding current of 20 to 40 mA, depending on loop resistance. It also lights an LED to give the user a positive indication that the telephone line is on hold. The 20 to 40 mA should prove sufficient to hold the majority.... -
This encoder uses a single contact per key keyboard and provides all other switching functions electronically. The diode connected between terminals 8 and 15 prevents the output from goitrg more than 1 V negative with respect to the negative supply Vss..... -
This indicator senses the switching on and off of the 48-V de line voltage and transmits the pulses to logic circuitry. An Hl1A10 threshold coupler, with capacitorfiltering, gives a simple circuit which can provide dial pulse indication, and yet reject.... -
The telephone-line decibel meter and line-voltage sensor shown lets you accurately monitor and adjust telephone sound levels. The 600-0 resistor properly terminates the line. .. -
This circuit can be used in telephone lines for speech activity detection purposes. This detection is very useful in the case of half-duplex conversation between two stations-in the case of siroultaneous transmission of voice and data over the same pair of.... -
This circuit is a bidirectional amplifier that can amplify both signals of a duplex telephone conversation. It uses the principle of negative resistance. Obviously, such an amplifier could easily be unstable; however, you can adjust Rl for maximum.... -
This recorder can be connected to the telephone lines just about any place, and no external power source is needed. The tape recorder"s switch terminals are applied to a pair of transistors, connected as Darlingtons, that are used to turn the recorder on.... -
Each and every time a phone on the same line or calling numberis taken off-hook, the circuit will be activated to control an external electronic circuit. If several extension telephones are used on one phone line, the circuit can be useful as a busy.... -
Q1 and Q2 are used to form the basis of an interface circuit for attaching a cassette recorder to the phone line. The circuit does not require a power supply because operating power is drawn from the telephone line itself. The incoming signal is fed across.... -
The IR transmitter connects to a telephone cir cuit, and transmits both sides of all telephone conversations to any line-of"sight location, within 40 feet. No !fOWer is taken from the central office, as long as all phones remain on-hook. The current.... -
Audio from the telephone is inductively coupled to the base of Ql. which is used as a preamp. The preamp provides a gain of about 75 dB, to boost the input signal from .about 4 mV to about 300 mV pk-pk. If you use a higher gain transistor, increase the.... -
Amplify or record a telephone call with the simple circuit shown. The 8-0 secondary winding of a miniature transistor output transformer is connected in series with either of the telephone lines. .. -
Tones (from the DTMF) on the telephone line are detected by Ul. When a valid tone is received, pin 14 (D.. -
This circuit switches a tape recorder via PL2. When on-hook, D5 conducts, turns on Ql, and cuts off Q.. -
This circuit flashes an LED to indicate that your phone rang during your absence. A differential amplifier with hyste.. -
If you are busy and cannot answer or do not wish to answer your phone, this circuit will give a busy signal without you .. -
The circuit requires neither a battery nor an ac supply to make it work. Set the recorder to the record position and .. -
This accessory connects to phone and will activate an attention-getting 120-V bell whenever a ringing voltage appears on the ph.. -
The circuit receives its power from a 15-V wall adapter (not shown). The circuit takes advantage of the fact that th.. -
The fax mate separates the fax machine from the phorie line, rings the fax machine on command, connects equipment to incoming lines, and senses the end of the message. When a touch tone pound signal (#) is detected, it actuates a ring greater and driver for....
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New Circuits
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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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