In the NMT system, where the positions of the mobile stations are maintained in memory, there may be occasions (e.g. restarts) when the memory becomes mutilated. In such a case the positions of mobile stations for which the affected exchange acts as an MTXH must be retrieved.
Since the affected exchange does not know the positions of its own mobile stations it sends a Restart Information Message (RES) to all MTX’s in the NMT network connected with No. 7 signalling.
The affected exchange resets the position of all its own mobile stations to the last known one.
The RES message may also be used in case all subscribers roaming from an MTX to a particular co-operating MTX (MTXV) are to be removed from the visiting register.
The MTXH that send RES will set the position of the subscriber in question to the last known position.
The exchanges receiving the reset signal will take the following actions:
i) It acknowledges the receipt of the RES by sending a Restart Acknowledgement Message (REA) to the affected exchange.
ii) It deletes the mobile stations, for which the affected exchange acts as MTXH, from the visiting register.
Note: The location Updating procedure is initiated in case of restart in MTXH, i.e. The MTX receiving RES is an MTXV.
Fig. 3.13 Restart Signalling procedure.