In this circuit R1 is 56 ohm and R2 is 220 ohm for the 110 V network. SCRs are according to the load. We found it in Philips 1968 documentation.
This filter, which rejects frequencies around 1 kHz, was found in the August 1993 Electronics Now...
This is a voltage regulator circuit for currents up to 1.5 A with an output voltage adjustment for outputs...
This circuit uses an operational amplifier that is still common today. The indication is made by...