We found this simple circuit in December 1975 Radio Electronics magazine. The integrated circuit is the 4009 CMOS, and the circuit works in both TTL and CMOS depending on the power supply.
We found this circuit in a 1977 publication for radio amateurs. It serves to test general purpose...
This circuit is from a 1998 Poptronics. The circuit triggers a buzzer after a certain time, waking...
This circuit for electronic voltmeter was found in a publication by Gernsback from 1960. The...