This two-transistor circuit was found in the September 1971 issue of Radio Electronics magazine. The sensor is an NTC and sensitivity adjustment is via R1.
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...