This circuit supplies a load at SO1 when the load at SO2 is powered. The circuit is from a Popular Electronics from the 90s. Diodes and triacs must match the loads.
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...