The Siemens 3RT1944-5AK61 is a SIRIUS magnet coil for Size S3 contactors, wired through screw terminals. It pulls in on 110 V AC at 50 Hz or 120 V AC at 60 Hz, with an operating range of 0.8 to 1.1 times the rated voltage — meaning the coil holds reliably down to about 88 V at 50 Hz and 96 V at 60 Hz, which matters when your control transformer sags under load out here in the grease.
Lifecycle reality — this one is done
This coil is a phased-out product. The manufacturer lists the lifecycle stage as 'current' in the sense that it's still a valid catalog entry, but the description flags it clearly: 'Phased-out product!!!' with the official successor being the SIRIUS 3RT2 series. If you're stocking spares for an existing panel, this coil works fine — just buy what you need now. For new builds or if you're planning a line-down swap, spec the 3RT2 replacement instead.