This circuit using the CK722 among others came out in a September 1950 Radio Electronics. It was one of the first circuits of this type published with transistors that started to reach the market.
This filter can be used to eliminate hum in sound equipment. Operational amplifiers can be 741 and...
This signal amplifier for ATV in the 427 to 439 MHz band was found in a magazine 73 for radio...
This simple three-LED sensor uses an NTC at the input. The circuit is based on an uncommon...