The Siemens 3RU2126-1DB0-ZX95 is a SIRIUS thermal overload relay, Size S0, CLASS 10. It mounts onto a contactor. The overload release is thermal (bimetal), with an integrated auxiliary switch that provides a signal contact for the control system — the note "for message Tripped" on the order code indicates the auxiliary contact is wired to report a trip condition, not just to drop out the contactor coil. Power dissipation per pole is 1.9 W.
Fastening method is contactor mounting — the relay snaps onto a matching Siemens SIRIUS contactor without tools. Mounting position is any orientation. Main circuit terminals are screw-type, accepting 2 × (0.5...1.5 mm²) or 2 × (0.75...2.5 mm²) solid or stranded wire. The screwdriver tip required is Pozidriv PZ 2 with a shaft diameter of 5...6 mm.
The integrated auxiliary switch is rated for switching at several common control voltages: 2 A at 24 V, 3 A at 120 V, 2 A at 230 V, 1 A at 400 V, and 0.3 A at 60 V. These ratings cover both AC and DC control circuits typically found in motor control centers.