This circuit uses an optical coupler called Raystor created by Raytheon in the 1960s. The circuit uses components from the era that can be changed. The current is low.
This narrowband data receiver is from the Philips Databook of 1990. The circuit is powered by 5 V...
This circuit was proposed by an old American documentation for listening to SSB stations. The...
This voltmeter for continuous voltages has several scales and is totally passive. The diodes are...