What it is and where it lands
CS1W-CRM21 is a Communications Module in the CS1W series, designed for backplane mounting in Omron CS-series PLC racks. It operates from 0°C to 55°C and carries approvals from CE, Lloyd, NK, and UL — the marine-class societies (Lloyd, NK) hint at a typical use in shipboard or heavy industrial control panels. Termination uses a rectangular connector plus screw terminals, so panel wiring expects both a ribbon or IDC header for the backplane bus and field wiring to the terminal block. The built-in display gives local status readback without a programming terminal.
Panel integration notes
Mounts on the CS-series backplane; rectangular connector carries the bus, screw terminals handle field wiring. Display gives local status during commissioning. Operating ambient range is 0°C to 55°C. No derating curve is provided; assume full load at 55°C.