The circuit for a spy phone bug transmitter is a secret listening device.
It has the ability to track and record phone conversations without the callers being aware of it.
These devices are referred to as transmitters or bugs.
Because these devices spy on peoples private conversations using them is wrong.
Also this type of circuits might be illegal in some nations.
Circuit Working:
Parts List:
| Category | Description | Quantity |
|---|---|---|
| Resistors | ||
| 47k | 3 | |
| 100Ω | 1 | |
| 22k | 1 | |
| 1M | 1 | |
| Preset 100k | 1 | |
| Capacitors | ||
| Ceramic 0.01μF | 1 | |
| Ceramic 330pF | 1 | |
| Ceramic 5.6pF | 1 | |
| Ceramic 10pF | 1 | |
| Ceramic 0.22μF | 1 | |
| Trimmer 50pF | 1 | |
| Semiconductors | ||
| Transistors BC547 | 2 | |
| Transistor BF494 | 1 | |
| Diodes 1N4007 | 1 | |
| Zener Diode 400mA 24V | 1 | |
| Coil L1 is built by winding 45 turns of 35 swg, super enameled copper wire over a 1M 1W CFR resistor | 1 | |
| Coil L2 is built by winding 3 turns of 21 swg, super enameled copper wire over a 12mm diameter air core | 1 | |
| Antenna | 1 |
The main objective of this telephone broadcaster or transmitter is to either spy on a phone call or act as a wireless telephone amplifier.
Particularly when there is no need for extra batteries or other power supply because this circuit gets its electricity straight from active phone lines.
This design saves money and space.
It uses very little electricity from phone lines providing continuously the outstanding operation.
A single IC type Veroboard can easily be used to create the little phone bug transmitter which fits neatly into a 3.75 x 5 cm telephone connection box.
There are two primary components to the spy phone transmitter: the FM transmitter and the automated switching part.
Resistors R1 through R3, preset VR1, transistors T1 and T2, Zener diode D2 and diode D1 are all part of the automated switching section.
R1 and preset VR1 work together as a voltage divider.
The voltage at the wiper of VR1 is adjusted from 0 to 32V with a telephone line voltage of 48V DC.
The Zener breakdown voltage and transistor T1s switching voltage are necessary for the circuits switching voltage.
Zener failure and T1 conducting happen when preset VR1 is adjusted beyond 24.7V.
As a result transistor T2 is switched off when the collector of transistor T1 moves toward the negative supply.
T1 is turned off by forward biasing T2 through R2 and providing a DC mode for T3 in the next FM transmitter section when the telephone handset is raised reducing the line voltage to around 11V.
The oscillator transistor T3 coil L1 and other parts are part of the low power FM transmitter section.
T2 serves as an electrical ON/OFF switch while T3 is a common emitter radio frequency oscillator.
Through T2 and its biasing resistor R3 the oscillator frequency is automatically controlled by the audio signal transmitted across the telephone lines.
The antenna then receives the modified radio frequency signal.
The telephone conversation is heard in distantly by tuning an FM receiver to the transmitter frequency.
Formula:
A spy phone bug transmitter is created by creating a small separate device that uses radio frequencies (RF) to wirelessly transfer sound to a receiver after detecting it in its surroundings.
Here are some key components and a summary for making a device like this:
Formulas and Things to Keep in Mind:
The carrier frequency (fc) of the RF transmission is usually chosen by the oscillator circuit when in use.
For a simple circuit the carrier frequency is generally calculated using the following formula:
fc = 1 / 2π√LC
where:
- L is the inductance of the oscillator circuit in henries H.
- C is the capacitance of the oscillator circuit in farads F.
Be careful to follow local rules on radiofrequency signal transmission before constructing or using a spy phone bug transmitter.
The rules have to particularly include license requirements, transmission power and frequency distribution.
The exact circuit design and component selection would be based on various factors such as range, power consumption and the form of modulation selected.
Conclusion:
The Spy Phone Bug Transmitter Circuit is a design of a hidden telephone transmitter that can be placed within a phone box.
It can function secretly since it is made to take power straight from the active phone lines without the need for an extra batteries.
The circuit is separated into two primary parts: the FM transmitter portion and the automated switching portion.
The transmitter is activated by the controlled switching portion when the telephone line voltage falls below a certain threshold usually during an active call.
By modifying the audio signals from the phone call into an RF carrier the FM transmitter parts enables an FM receiver tuned to the same frequency to remotely pick up the intercepted conversation.
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