This circuit was obtained from a 1967 General Electric manual. The circuit uses components of the time, but equivalents can be used, for example, a BC547 for the transistor and a TIC106 for the SCR.
This circuit of a 1969 Electronic Design uses RTL logic. The setting can be adapted to TTL. The...
This circuit can be found in other projects in this site. When S1 is open the circuit produces...
This interface shield circuit is from the 1983 Intersil Databook. The components used are uncommon...