The Attach/ Detach» indication is stored in the HLR/MTXH and in the MTXV. The default value is «Attach» in the HLR/MTXH and «Detach» in the MTXV.

The «Attach/ Detach» indication in the HLR/MTXH is the master indication. The indication in the MTXV is used to trig Supplementary Updating message (SUM).

In case data can not be trusted, e.g. after reload of data, the «Attach/ Detach» indication shall always assume the default value in each affected node.

Detach is initiated by a special signalling scheme sent to the MTX from the mobile station.

• At reception of the «Detach indication» in the MTX, the subscriber is marked «Detached».
• The HLR/MTXH is notified of the «Detach indication» with a Supplementary Updating message (SUM).
• At reception of the Supplementary Updating message (SUM) including a «Detach indication», the HLR/MTXH marks the subscriber «Detached» from the network and responds with a Supplementary Updating Acknowledge Message (SUA).
• Any incoming call to the mobile station, while marked «Detached» in the HLR, is treated as if the mobile station does not respond to paging.

In the MTX, the subscriber is marked «Attached» at detection of any activity from the mobile station, e.g. location update, message polling, call from the mobile station.

• When the mobile station is attached the HLR/MTXH is notified with an «Attach» indication in a Supplementary Updating message (SUM).
• At reception of the Supplementary Updating message (SUM) including a «Attach indication», the HLR/MTXH marks the subscriber «Attached» in the network and responds with a Supplementary Updating Acknowledge Message (SUA).

In case the mobile station has changed location at registration, the LUM sets the «Attach/ Detach» indication in the HLR/MTXH to «Attached».

The procedures are described in the following figures.

Figure 3.17a Detach indication procedure

Figure 3.17b Detach indication clearing procedure.