Hello everyone,
as I didn't have any direct help from the forum, I had to keep doing tests, finally with a simple sound card (usb) connected to the PC, a direct audio cable from the rrc-control to the sound card and a rj-45 to 3.5mm mono jack with pin 6(mic) and pin 5(ground mic) connected to the ic-7100 control on the sound card, works perfectly. special thanks to EA3IGY for helping me find my way.
Glad if this info helps any of you.
73 of Edward.