FM RADIOTransmitter Bug Circuit Diagram FM Transmitter Block Diagram Spy Bug FM Transmitters, big FM, spy microphone, FM  Transmitter circuit FM RADIO TRANSMITTER BUG CIRCUIT  uses a Hartley type oscillator. Normally the capacitor in the tank circuit would connect at the base of the transistor, but at VHF the base-emitter capacitance of the transistor acts as a short circuit, so in effect, it still is. The coil is four turns of 18swg wire wound around a quarter inch former.  The aerial tap is about one and a half turns from the supply end. Audio sensitivity is very good when used with an ECM type microphone insert. FM Transmitter Bug using with BC548 Transistors.

Surge Protection Circuit for Power Supply The surge Protection circuit  is simple with timer IC and it can give an effective solution for protecting your valuable and sensitive electric/electronic systems. Surge typically occurs when power returns after a power-cut (blackout) and connected equipment receives a surge of electricity at an over-voltage level, which can be very damaging. SURGE PROTECTION CIRCUIT Usually, power-back surges are created by the utility, when it restores supply at an above normal voltage level in order to compensate for the demand as connected equipment restarts at the same time. The author took this little circuit personally to protect numerous lab equipment. The  Surge Protection circuit  is designed to be constructed in a small module structure with an onboard electromagnetic relay as the primary switching device. The design is centered around (again) the famed 555 timers, wired as a bi-polar latch switch with its two comparator inputs tied tog...

EXTENSION BOX WIRING AT HOME Presented here is an instructable to  Make Your Own Electric Extension Board.  In this video step by step instructable, I will show you wiring in the Extension Board. Create an extension box in your home which is cheap but very good for Digital Set Top  Box  to the audio system, computer to any other device running on electronic  power. Material Required for Electric Extension Board Plastick Switch Board  3-Pin Socket 2-pin Socket 3-Core Cable Tags:  how to make electric switch board

This circuit provides a delayed visual indication when a door bell switch is pressed. In addition, a DPDT switch can be moved from within the house which will light a lamp in the door bell switch. The lamp can illuminate the words "Please Wait" for anyone with walking difficulties.  A Doorbell for the Deaf Circuit Diagram : Notes : The circuit uses standard 2 wire doorbell cable or loudspeaker wire. In parallel with the doorbell switch, S1, is a 1N4001 diode and a 12 volt 60mA bulb. The bulb is optional, it may be useful for anyone who is slow to answer the door, all you need to do is flick a switch inside the house, and the bulb will illuminate a label saying Please Wait inside the doorbell switch or close to it. The double pole double throw switch sends the doorbell supply to the lamp, the 22 ohm resistor is there to reduce current flow, should the doorbell switch, S1 be pressed while the lamp is on. The resistor needs to be rated 10 watts, the 0.5 Amp fuse pr...

In many circuits we need to generate an internal adjustable voltage. This circuit shows how it is possible to use a trusty old NE555 timer IC and a bit of external circuitry to create a voltage inverter and doubler. The input voltage to be doubled is fed in at connector K1. To generate the stepped-up output at connector K2 the timer IC drives a two-stage inverting charge pump circuit. The NE555 is configured as an astable multivibrator and produces a rectangular wave at its output, with variable mark-space ratio and variable frequency. This results in timing capacitor C3 (see circuit diagram) being alternately charged and discharged; the voltage at pin 2 (THR) of the NE555 swings between one-third of the supply voltage and two-thirds of the supply voltage. Voltage Inverter Circuit Using IC NE555  The output of the NE555 is connected to two voltage inverters. The first inverter comprises C1, C2, D1 and D2. These components convert the rectangular wave signal into a nega-tive DC leve...