This circuit was found in 1980's Radio Electronics. The circuit produces a 1500 Hz modulate 35 kHz. The components used are still common.
This oscillator takes advantage of the 2000 ohms headphone inductance as the oscillator circuit coil....
This circuit was found in an 80's Electronic Engineering. The circuit uses a multivibrator with...
Found in a 90s Radio Electronics, this circuit is intended to trigger a relay when the current in...