This 5-tube hi-fi amplifier was found in an American publication from 1947; The output is in class B and the circuit uses a source with transformer.
The figure shows how to control the blinking of a 5 V blinking LED with an LDR. The LED only...
Suggested by Maxim in documentation from the 90s, this circuit has its response curve given next to...
This circuit is from a 1965 General Electric publication. It uses a thermistor to fire a reed...