This circuit simulates a resistor controlled by digital signals. We found it in American documentation from the 90s. The basic component is a CMOS 4016 or 4066 digital switch.
This experimental amplifier was found in the 1960 Mullard transistor reference manual. The...
This circuit from Motorola is from 1968, appearing elsewhere on this site. The transistors admit...
This circuit triggers the LED when the monitored battery voltage drops below 9 V for 12 V...