Found in American documentation from the 90s, this circuit uses a high voltage relay and has no grid isolation. The high values of R1 and R2 prevent the shock when it touches the sensors.
This control stage or shield can be used with motors from 3 to 12 V and currents up to 3 A....
This simple bench source uses only transistors and can supply up to 500 mA with a BD135 for TR2....
This configuration, already found in other articles in this section and on this site, was obtained...