Found in a 90s Popular Electronics, it serves both TTL and CMOS logic. The injector can provide 10 kHz or 100 Hz signals. The circuit drives a transducer and two LEDs.
This circuit using components that are still common in our market was found in a 1987...
This circuit is based on the well-known PLL 567 and can operate at 100 kHz. The transformer can be...
The simplest flip-flop can be built with two NAND gates as shown here. This is a Reset-Set [S-R]...