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.
This SCR relaxation oscillator was found in an 80's Electronic Design. It flashes a small...
We found this shield circuit in a 1991 technical documentation. The phototransistor can be...
This circuit for old photo enlargers was found in a 1970s RCA manual. The components are from the...