This circuit was found in Motorola's Linear Interface ICs of 1993. The integrated circuit used is not common and the load current depends on the Triac.
This Signetics circuit uses a double 555 (556) to generate tone bursts at frequencies determined by...
The accuracy of this circuit depends on adjustments made with capacitors of small tolerances of known...
Found in a Motorola documentation from the 70s, this circuit makes use of transistors of the time....