We found this circuit in an 80's Electronic Design. It makes use of couplers of the time that can be replaced with equivalents.
We found this circuit in Radio Electronics magazine. It triggers a load (relay) by the noise from...
We found this circuit in documentation from Ferranti from 1968. The circuit uses transistors from that...
This circuit was obtained in a 1976 magazine. We can use the 555 and another BC548 to generate square...