The emergency services have come to rely on certain features of the traditional telephone system to enable them to do their jobs and to safeguard against misuse of the general public’s privilege to call them night or day. The key feature is the Caller Line Indication (CLI). This is a number unique to every telephone line attached to the public network and it is possible to trace the location of the telephone that made a call from the CLI.
The CLI enables fire and ambulance services to locate where they are needed should the caller be unable to tell them; they may be too young, old or infirm to do so. The CLI enables the police and security services to locate the source of criminal use by using the telephone network. Meanwhile location can be ascertained on the mobile network through tracing the call to the base station to which the mobile phone is connected.
On the other hand, an IP telephone is recognised not by a CLI, but by its IP address which as no geographic meaning. Indeed one of the advantages of VoIP is that wherever in the world an IP phone connects to the Internet, the Internet will find it to deliver the call. Given this, the emergency services will have no idea from where the call originates schlüsseldienst in der nähe.
Currently, most VoIP solutions carry calls between company locations and calls to the public telephone network are made via a gateway, such as those provided by VegaStream. In this scenario, the problem for identifying the location of a phone is similar to that faced when a company uses a traditional PBX solution, although most responsible companies have implemented an appropriate solution by mapping their IP phone addresses to a traditional list of extensions.
VoIP systems can connect to the public telephone network via Internet Telephone Service Providers (ITSP). ITSPs offer significant reduction in call charges by carrying what are the expensive elements of the phone call over the Internet.
For example, an ITSP customer’s call from London to Edinburgh is carried from London to a local switch in Edinburgh via the Internet. Just the final leg of the call is made over the traditional telephone network. As far as the CLI is concerned, the call is being made from the local switch in Edinburgh to the end-point, while the actual origin of the call is completely unknown. If the ITSP customer were simply calling the local fire brigade, the call would travel over the Internet to the ITSP who would then make the connection to the emergency service from its own public network gateway. From a CLI perspective, the call to the emergency service would appear to come from the ITSP.
VoIP and Power
The traditional telephone network is self powered. If the general power supply goes down as it often does in an emergency, the phone system will still work as the phone companies have extensive uninterruptible power supply (UPS) contingencies. VoIP systems require an external power source, and if the power fails, unless the user has implemented their own UPS solution, the phones will not work.
The Immediate Solution
To ensure emergency cover, VoIP system users, at this time, need the contingency of at least one traditional telephone line. VegaStream gateways’ feature a pass-through facility which can be programmed to automatically make and receive calls over this line in the event of power failure. The gateway can also be programmed to automatically route 999 emergency calls over this line to ensure the emergency services receive the vital CLI information.
The Long Term Solution
There are a number of national, supranational and industry wide initiatives to establish and implement standards for geographic recognition of IP telephony equipment to meet the requirements of the emergency services. The large national phone companies that are in the process of converting their traditional phone networks to VoIP are actively involved as they too have a vested interest. Furthermore, in the enterprise space, responsible systems integrators will ensure that CLI information is available both to assist the emergency services and to meet basic requirements of good citizenship and good business.