The Siemens 5TT5042-2 is a SENTRON Insta contactor with 2 normally-open and 2 normally-closed contacts, rated for 400 V AC and a 40 A switching capacity. The coil is 24 V AC/DC, so it works with either supply — no separate coil voltage variant needed for mixed-control panels. At 3 modular width units (roughly 53.5 mm wide), it snaps onto a DIN rail inside an enclosure. The IP20 rating means it's protected against finger contact but not moisture — keep it inside a cabinet, not on a washdown line. The 71 mm depth (64 mm installation depth) fits standard 80 mm deep enclosures, but the manufacturer notes that spacers are required between units for heat dissipation — don't pack them tight without air gaps.
Contact configuration and coil drive
The 2 NO + 2 NC contact arrangement gives you one set for the load and one for a feedback signal or interlock, without adding an auxiliary contact block. The 24 V AC/DC coil draws 4 W per pole in hot operating state at rated current — factor that into your power supply budget if you're running several contactors in a row. The coil accepts both AC and DC, so a single 24 V power supply can drive the whole panel. No need to run a separate AC control transformer just for this contactor.