High isolation telephone ringer


Posted on Nov 12, 2012

The diode rectifies the ringing signal to supply the operating power to the audio relaxation oscillator made up of LI, L2, Rl, R2, and C. Moreover, L2 together with Ql acts as an opto-isolator, totally isolating the telephone line from the rest of the circuit. The oscillator audio frequency is optically coupled to the photo-Darlington which drives Q2 and thus the speaker.


High isolation telephone ringer
Click here to download the full size of the above Circuit.

The 10 µf capacitor is not large enough to smooth the ringing ripple completely. This results in frequency modulation of the audio oscillator giving it an attention-getting warble.




Leave Comment

characters left:

igt gas safety device price   Jun 5, 2018

Really nice post. Thanks for sharing this informative post. gas safety device price in Hyderabad

New Circuits

.

 


Popular Circuits

Pocket-sized geiger counter
Water Activated Relay circuit board
phototransistor Light sensor using Photo Transistor
7 2V Battery Replacement Power Supply For Camcorders
1 watt PLL portable fm transmitter circuit
Digital Ber-password circuit
High Power Square Wave Generator (0-500V 25A)
IR Remote Control Receiver
Double astable multivibrator circuit diagram



Top