This circuit was published in an article in Radio Electronics magazine in October 1988. It uses components that are still common today, except for the sensor, which is a special type from that time.
This circuit had its assembly described in a Radio Electronics from March 1963. The circuit uses 2...
We found this configuration in a documentation for radio amateurs from 1974. The circuit can be...
We found this circuit in an English documentation from 1989. The integrated circuit used is not...