[SR-Users] Clients are busy

Hello Community, in my scenario works multiple user with the kamailio server and uses different clients. They work in a mobile scenario and setup the clients and break the clients in a high period. If they break the clients, sometimes they don't send a bye, but they take off the cable connection during a call. If these devices will connected again and other clients try to call them, they are busy. That is my problem :). Does the Kamailio server provides any function to send a bye message if a clients don't register at a required time? Or is there another solution available? Thanks for help. Cheers, Kai