This circuit was obtained from an Electronics Now from the 90's. It generates the dial signal and the ring tone, serving for testing as well as for demonstrations.
This circuit is from the 1977 RCA Linear Integrated Circuits Manual. The circuit has a...
This circuit was found in 1980's Radio Electronics. The circuit produces a 1500 Hz modulate 35 kHz....
The maximum power of the controlled load depends on the triac used. The circuit is from a Radio...