This circuit was obtained from Dutch documentation from 1967. It uses transistors of the time which can be the BFY50 and 51 for the output and the BC series for the others.
This circuit was obtained from a 1986 Spanish magazine Resistor. The magazine no longer exists, but...
This circuit was found in a 90s American documentation. The circuit uses an LED that can be of a...
This circuit is from a 1974 Ferranti transistor manual. Transistors are general-purpose types at...