Using the 723 integrated circuit, this circuit was found in an article on power supplies in the August 1971 Radio Electronics magazine. The transistor may be the BD136 on a heatsink.
This oscillator was found in a 1976 documentation. The no specified components indicate circuit...
This circuit activates a buzzer when the voltage applied to the input falls below a preset value in...
This protector was found in an Electronics Now from the 90s. The 250 V transient suppressors are common...