This circuit is from old documentation, using a component that cannot be found easily today. The indicator is a galvanometer, and the input voltage is in the order of 1 V.
Originally in 1986, this circuit was developed to operate with microcomputers of the time like the...
This unusual configuration, but which has already been explored in other articles, uses diodes in the...
This 1992 circuit demodulates FSK signals by providing TTL-compatible logic output. The...