This two-tone alarm siren was found in the January 1975 issue of Radio Electronics magazine. The power transistor can be changed and with it, Rx has values from 10 to 47-ohm.
This circuit is from Radio Electronics from March 1977. The integrated circuit is from that time...
This 1.2 to 32 V x 3 A regulator was found in an 80's EDN. The power components must be equipped...
This power control from Motorola's 1971 SCR Power Control Fudamentals can control full wave loads...