This 5 V power supply for TTL, Shields and microcontrollers is old, and the components can be replaced by modern equivalents. Transistor Q1 can be a TIP31 and Q2 can be a BD135.
Featuring low output impedance and high input impedance, this configuration was found in a 1980s...
In the figure we have a TTL logic interfacing circuit as CMOS logic using a 6N139 optocoupler...
We found this circuit in an English documentation from 1989. The integrated circuit used is not...