This circuit was obtained from a Philips documentation from 1968. The transistors can be replaced with equivalents, only with care so that the doubles are exchanged for matched pairs.
This circuit is basically the same configuration as the previous one with a power stage with...
This power control from Motorola's 1971 SCR Power Control Fudamentals can control full wave loads...
This circuit was found in a 1980s documentation. The indicated integrated circuits are uncommon...