This resistance meter was found in an English documentation from 1989. The operational amplifier admits an equivalent and the transistor can be a BC558 or BC559.
This circuit was found in a 90s Radio Electronics. It produces an ultrasonic signal in a special...
This circuit can generate signals in the audio range between fraction of hertz up to approximately 10 kHz...
This circuit is from a 1967 publication. The configuration holds true for modern transistors having...