Audio and Visual Telephone ringer


Posted on Mar 21, 2013

Many a times one needs an extra telephone ringer in an ad joining room to know if there is an incoming call. For example, if the telephone is installed in the drawing room you may need an extra ringer in the bedroom. All that needs to be done is to connect the given circuit in parallel with the existing telephone lines using twin flexible wires. This circuit does not require any external power source for its operation. The section comprising resistor R1 and diodes D5 and LED1 provides a visual indication of the ring. Remaining part of the circuit is the audio ringer based on IC1 (BA8204 or ML8204). This integrated circuit, specially designed for telecom application as bell sound generator, requires very few external parts. It is readily available in 8-pin mini DIP pack.


Audio and Visual Telephone ringer
Click here to download the full size of the above Circuit.

Resistor R3 is used for bell sensitivity adjustment. The bell frequency is controlled by resistor R5 and capacitor C4, and the repeat frequency is controlled by resistor R4 and capacitor C3. A little experimentation with the various values of the resistors and capacitors may be carried out to obtain desired pleasing tone. Working of the circuit is quite simple. The bell signal, approximately 75V AC, passes through capacitor C1 and resistor R2 and appears across the diode bridge comprising diodes D1 to D4. The rectified DC output is smoothed by capacitor C2. The dual-tone ring signal is output from pin 8 of IC1 and its volume is adjusted by volume control VR1. Thereafter, it is impressed on the piezo-ceramic sound generator.





Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

Talking Frog Box using PIC16F870
Loudspeaker Box Amplifier schematic
Pulse-Width Modulator
ceiling fan regulator motor speed
automatic street light control system
Solar Cell Voltage Regulator
Technical Proposal for Subcutaneous Transmitter
555 tri-state acousto-optical logic circuit



Top