Found in a 90’s American documentation, this circuit indicates the frequency of input pulses up to 1 kHz. The circuit has a very explored configuration on this site.
The operational amplifier of this balanced circuit is old and can, however, be implemented with...
This SSB modulator does not use the balancer transformer. The circuit is from an 80's...
In the figure we show a configuration for a crystal controlled overtone oscillator using a...