Found in a 90s Popular Electronics, this circuit excites a 40 kHz ultrasonic transducer. The transistor can be a BD135 or other medium power.
This circuit was found in an 80's documentation using an NE5514, operating at the time. The font...
This circuit generates sinusoidal signals between 300 and 3000 Hz. We find a 303 Circuits from the 90's....
This circuit from a 2003 documentation, has a protection system that disarms the power supply if...