Recommendation H.460.20 consented at the last Study Group 16 meeting solves the problem of how to provide location information in calls generated to/from H.323 systems. The Recommendation allows these systems – such as VoIP or videoconferencing – to convey information that could be a URL, an e-Mail, a postal code, or a mobile telephone number. This is much more than can be achieved with a traditional public switched telephone network (PSTN) call.

Currently calls generated or terminated in H.323 systems do not carry - end-to-end – details of where that call is coming from. This information is needed by the public switched telephone network (PSTN) for emergency services, more accurate billing and for routing the call. Additionally it is useful, for instance, in applications such as telemarketing where calls can be routed according to their origin. 

Technically H.460.20 gives H.323 the ability to convey the location number present in ISUP – the system that determines the set-up, co-ordination and taking down of calls. Without this ability location information is lost at the interworking edge between the IP network and the PSTN. An additional benefit is that it simplifies interworking with the session initiation protocol (SIP).