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

Bridging Adapter For Power Amplifiers
Power Supply Current and Voltage Regulated By LM317 or LM350
Basic RF Oscillator circuit diagram
3V to 40 Volt DC Converter Circuit
Nescaf mod
Interfacing LCD via SPI
question about ceramic resonator
parallel inverter
Metal detector 8
Metal detector circuit diagram 1
Video circuits
AC contactor silent operation of the circuit
TA7366 67 five lights single drive circuit
HD a 3A limit energy-saving three-phase power protection circuit