any body knows the Siemens Digital set optipoint 500 connections,i have the USB adapter model S30817-K861-A301-5, i need to connect this set to the Siemens 1120 (i dont have digital card), any help available thanks

You need a digital card to make a digital phone work. The usb connection is to connect the phone to a PC. This connection allows you to use Microsoft TAPI for dialing on the PC.

You could also use the OptiPoint 500 digital telephone adapter, it slides into the bottom of an OP500 telephone and lets you add an additional OP500 that way, same as the headset adapter or analog adapter. But as Booper said, the USB will not support a digital phone off of it.

Steve