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 has a frequency range of 30 Hz to 100 kHz with an output signal of 1 Vrms. We found...
This circuit is suggested by the Optoelectronics Sourcebook by Texas Instruments when AC signals...
This sequential relay actuation system circuit for traffic lights was found in Electronics Now...