With an 18 V input, this regulator was found in Philips documentation from the 60's. The transistors are from that time. The power transistor must have a heatsink.
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...