This input circuit for an oscilloscope was found in Radio Electronics from the 90s. The operating circuit is from that time, and a modern equivalent can be tried out.
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...