Vox box

Posted on May 2, 2012

The electronic circuit in the VOX Box consists of three parts: a microphone preamplifier, a Schmitt trigger, and a relay driver. Input signals (MIC INPUT terminals) to the microphone preamplifier (Ul) are amplified and fed to a THRESHOLD control (R8). When the preselected threshold voltage level is exceeded, the output of the Schmitt trigger (U2) immediately goes high. The signal from U2 is rectified and the voltage developed across C7 turns on the relay energizer transistor (Ql).

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

That transistor action passes pull-down current through the coil of relay Kl. The changing of the relay SPDT contacts can be used to either make or break an external ac or dc circuit.

Leave Comment

characters left:

New Circuits



Popular Circuits

Stereo Headphone Amplifier
123 Game - All MCU-free
theremin as a capacitive sensing device
chip programmer
A Simple Keypad Using Lin With The Mc68hc908qt/qy Mcu
40 MHz Wideband RF Amplifier
Temperature Conversion circuit
Five uses tri-state logic audio pen CD4066 555
15W Valve Modulator Amplifier circuit