5V Dial Tone Circuit Circuit


Posted on Jul 24, 2012

This circuit uses inexpensive, common components to generate a precise dial tone for phone applications (see the figure). Ul (an Intel 82C54 timer-counter) generates 350 and 440Hz square waves that are filtered by Rl/Cl and R,JC2, and mixed together by resistors R2 and R4. An operational amplifier configured as a 395-Hz, Sallen-Key, second-order bandpass filter (halfway between 350 and 440 Hz) removes unwanted signal harmonics.


5V Dial Tone Circuit Circuit
Click here to download the full size of the above Circuit.

Almost any timer-counter can be used as the signal source, so long as it produces roughly square-wave outputs.




Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

Overtone crystal oscillator
Ranging-system
Efficient Power Booster
Fast Low Duty-Cycle Pulse Oscillator
Automatic blind hooked up to existing projector screen using Arduino
Simplest and low cost USB AVR
Simple IR audio link
Preamp Mixer Stomp-Box for Dobro Guitar
iPod FM Transmitter
A high-power DC motor overcurrent protection circuit
A multi-channel pulse distributor circuit



Top