Category Archives: Audio and Music

Simple Door Intercom

Posted on April 19, 2011 by Rend

This intercom circuit suitable for accompanying  door bell. This circuit uses the speakers both as microphones and as loudspeaker. This intercom is made simple by using only a single amplifier IC LM390 to serve two-way communication. This circuit is based … Continue reading →

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High-Q Notch Filter with Active Twin T Network

Posted on March 13, 2011 by Rend

This is a circuit of High-Q Notch Filter. This circuit consist of LM102 and a twin “T” network. Twin T network sum two signal from different path with different phase shift. At certain frequency, the phase shift will be 180 … Continue reading →

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VOX (Voice-Operated Switch)

Posted on March 5, 2011 by Rend

This schematic diagram below show a circuit of VOX Box (voice-operated switch). This circuit consist of a Schmitt trigger, a relay driver, and microphone preamplifier. The microphone preamplifier(U1) receive input signal which will be amplified. THRESHOLD control (R8) is fed … Continue reading →

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