The LD-C101 is a USB-to-CI-V interface adapter used to connect a computer (via USB) to Icom radios' CI-V (control) serial bus for CAT control, command/response, and automation. It provides USB virtual COM port connectivity and signal-level conversion appropriate for Icom CI-V protocols.
If you need the circuit design paper:
If you have a working radio, send FE FE 5E E0 03 FD (read frequency) to COMx. The radio should respond. Use a tool like CI-V Commander or Hamlib: Ld-c101 Usb To Ci-v Driver
rigctl -m 103 -r COM5 -s 19200 f