General

It shall be possible to make emergency calls from every extension in the system, and it is essential that all extensions, independent of Traffic Connect Class and extension type, are configured to allow calling emergency numbers.

This document describes configuration of IP extensions, both SIP and H.323, in the correct way for emergency call handling.

All other extension types shall be configured accordingly. One of the primary concerns around emergency situations involving calls from IP telephones is the fact that the calling user may reside, at the time of making the emergency call, anywhere on the corporate LAN/WAN. The standard method for the dialed emergency center to find the physical position of the calling user is a database look-up with the Calling Line Identity as identifier. Using IP, this may give a completely wrong address and direct the emergency team to another part of the country.

The CLI of an IP extension does not necessarily give the correct location as the user may have logged in at any corporate location, served by the same IP PBX. Emergency calls from such a location must have a CLI that can provide the correct address to the office in question and it may also be required that the call should be routed to a local emergency center.

The MX-ONE solution for emergency calls is based on the telephony domain concept. Per telephony domain, a DID number in the range that covers the applicable office is reserved for emergency call purposes and is delivered as CLI when emergency calls are made from any IP-terminal connected in that domain irrespective of which user that is making the call.

The emergency call data per domain is specified with command and includes the directory number of a virtual extension (with a special type ‘emergency call back’), the CLI that shall be sent to the emergency center.

The virtual extension is used for call-backs from the emergency center. This virtual extension will forward incoming calls to the last telephone making an emergency call from this domain. This call forwarding is active for 30 minutes after the last made emergency call.

In situations where calls from a specific domain need to be routed to a local emergency center, the local area code valid for users in a specific domain can be automatically inserted between the LCR access code and the dialed local number. The LCR functionality is then used to route the call to the correct emergency center.

In situations where there are several emergency centers with the same area code, a dummy area code can be defined for each local office.

However, this requires careful configuration of LCR data as the correct area code needs to replace the used dummy code for all non emergency calls.

Note that for IP users having the home area code configured (via the extension command or web GUI), the home area code is not used for emergency calls.

The ELIN, Emergency Location Information Number, is supported for the Mitel 6800/6900 phones, and a similar function is also supported for H.323 DBC 4xx phones. Note that in some markets, the ELIN must be a DID number in the PBX number plan, to make it possible to call back from the public alarm center.

In addition to the ELIN (which is conveyed as caller name or number), the system also supports conveying of emergency Location Identity via SIP trunk, in the form of a PANI Header (Private Header Access Network Information), according to RFC 7315 and ES 203 178.