This 1968 Mallory circuit uses an uncommon integrated circuit today. The circuit has a 30 to 20,000 Hz response with lower power and is powered by 12 V.
We find this circuit in an old documentation, but it can be implemented with modern equivalent...
This circuit eliminates transients that are 10% above the zener voltage. The transistor must be in...
A solution for using more than 6 channels in a tone-modulated system that uses LM567 as decoders, is to...