This circuit, to control air conditioning systems, was found in July 1984 Radio Electronics magazine. The circuit is for old types of the time that did not have microcontroller control.
This high-gain digital amplifier uses general-purpose transistors. The supply voltage is logic...
This 1968 Hughes circuit uses period components and operates at 8 Hz. Current equivalent...
This circuit is from the time of the tubes, being indicated to operate with transmitters turning off...