The present invention relates to the field of mobile telephony networks and more particularly to a device, a system and an associated method for ensuring continuity of telephony services on the network. The invention is based on the use, as a temporary backup for faulty HLR equipment, of HLR equipment possibly initially empty of any user data and which, during location demands from non-referenced subscribers, on its own initiative actuates the CIS information system in order to recover a minimum of data allowing identification of the subscriber on the network and therefore his activation. No synchronization with the active HLRs is necessary since the data are recovered as necessary on the information system. In addition, the updating data traffic between active HLRs and backup HLR is avoided.