This circuit is from a 1964 Electronic Design. The sensor is an LDR and the transistors are general-purpose types. The circuit triggers when the light that falls on the sensor is cut off.
The circuit is from an Electronics Hobbyst Handbook from the 90s, being valid for panels of the...
This circuit can generate signals from 80 to 800 Hz with an amplitude of 0.3 V. We find it in a...
This circuit is from an American publication from the 60's. The power is on the order of 600 mW....