Within 60 seconds of being on a desk phone call, the MDA-200 will jump to PC mode. I’m using a Plantronics APC-41 EHS cable with my Cisco phone. Why does this happen?
Any time there is an APC-41 EHS cable plugged into the back of the MDA200 it will need a solid connection path to the AUX port of the Cisco 79xx series phone. If this connection is disrupted or not present, the "handshaking" between the MDA200 and the Cisco phone/EHS cable will not occur, which causes the MDA200 to switch back to its default state (i.e., PC mode).