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Ensuring accurate and reliable 999 location identification for 999 calls is not a new problem for private telephone networks. However, it has become a significantly bigger and more complex problem as legacy TDM PBXs are progressively replaced by IP-PBXs.

It is relatively straightforward to design a private telephone network based on TDM PBXs to deliver accurate and reliable 999 location information.

A TDM PBX network is characterised by having individual PBXs at each site.  These can be configured to intercept 999 calls and route them via a local public telephone network connection. This ensures that the correct location information is presented to the 999 operator.

In contrast, a private telephone network based on IP-PBX technology would comprise a single PBX server connected via the internet to remote sites. All external calls, including 999 calls, would exit the private telephone network at the PBX server location.

This is a very cost effective network design, but it causes significant problems for identifying the location of 999 callers. The location information presented to the 999 operator would be that of the PBX server which would typically be the organisation’s head-office or data centre.

It is technically possible to implement local public network break-out points at each site on the network, but this would be costly and complex and would remove one of the key benefits of an IP-PBX based private telephone network.

A further complication is that IP-PBX based private telephone networks typically serve many more sites than their TDM predecessors. The reason for this is that it is relatively easy and inexpensive to incorporate small branch offices into an IP-PBX based private telephone network when compared to TDM PBX networks. All that is required to connect a small branch office to the corporate IP-PBX network is an internet connection

It is clear therefore that IP-PBX based private telephone networks require a different solution to the problem of providing accurate and reliable location information for 999 calls.