What it is and what it does
The Siemens 3RH1921-2CA10-ZW98 is a front-side auxiliary switch that adds one normally-open (NO) contact to a 3RT1 contactor. The spring-type (cage-clamp) terminal accepts solid or ferruled stranded conductors up to 2.5 mm² — no screwdriver torque check needed on the line, which saves time in high-density panels where access is tight.
