This circuit was suggested by a 1967 Electronic Design. Modern equivalent transistors can be used.
Common operational amplifiers like the TL series, CA3140 and others can be used in this circuit...
This high-gain amplifier was found in the March 1994 issue of Electronics Now magazine. The...
We found this timer for times of a few minutes in a 1974 Ferranti transistor manual. The relay is 37...