This circuit uses a 100 kHz crystal, but nearby frequencies can be obtained with appropriate crystals. Components are still common today.
Found in a 90s Popular Electronics, this sensor operates by infrared reflection. The components are...
This simple PWM circuit was found in the March 1991 issue of Radio Electronics magazine. The...
This flasher was found in an old Hands On, but uses common components. The optocoupler can be...