The Omron CRT1-ID16SY-1 is a 16-point digital input module in the CRT1 remote I/O series. It takes 16 discrete signals from field devices like limit switches or proximity sensors and passes them back to the controller over the CRT1 backplane bus.
This module mounts on a CRT1 slice I/O rack. It's used in distributed layouts where you need a local input bank near the machine rather than pulling every wire back to a central PLC cabinet. The CRT1 series is common in Omron Sysmac and CJ/CS setups for mid-size lines.