A method is provided for operating an RF transponder system to detect the presence of an RFID device in the proximal space of an RF reader unit having an excitation signal generator circuit and an RFID device detection circuit.

Here is a HID patent! By blogging this patent I am teaching you about technology that is patented by HID. By hosting this patent Google is also teaching you about technology that is patented by HID. Hey, HID, why don't you sue me?

Detection of an RFID device by an RF reader... - Google Patents