This traditional configuration with the 555 was obtained in an 80s Hands-On Electronics. The relay is of the sensitive type according to the supply voltage.
This low power circuit for the FM band was found in a spy book from the 90s. The tunnel diode is...
This 3-decade operating range VCO was found in a 90s Popular Electronics. The circuit uses...
This circuit was found in an Electronic Design from the 90s. Operational amplifiers admit modern...