A location register for a mobile communications network is coupled by an SS7 network for passing messages, has a mated location register at a different location to provide geographical redundancy, and has a status detector for detecting a status of the associated register, by sending a heartbeat message to the associated register. It deduces a fail if the message is returned by the signaling network. A cutover manager is arranged to enable a cutover on the basis of at least the detected status. By providing a more positive detection of a failure than merely passively interpreting a lack of response to the heartbeat, false triggering of cutovers owing to transient failures or temporary congestion, can be reduced. The cutover manager can verify the status by sending other messages by other routes, or using other criteria.