This control for 1/15 HP motors with 5,000 rpm for 115 V power grid was suggested by a Motorola circuit manual from 1968. The SCR supports more modern equivalents.
The transistors are 2N918, 2N3464 and other RF equivalents of the time for Q1. For Q2, 2N3399, 2N2894...
This circuit, which can be used as a shield, was found in a 90s Electronic Design. The circuit...
This interesting intercom circuit was obtained from an Argentine publication from the 1970s....