Providing access to dial the emergency services has been a controversial issue for all IP-based telephony. Users may see a phone and want to use it to make such a call. Anybody installing phones should contemplate what happens in this situation.

The first thing to note is that not all organizations route emergency calls to the publicly operated emergency call center. Some large organizations and universities route these calls to their internal security office. The suitability of this approach depends on local laws and the training of the security staff.

Many SIP providers now offer an option to handle emergency calls. For this to be effective, the SIP provider usually needs to have accurate records of the addresses where the SIP trunks are used. For example, care needs to be taken to ensure that emergency calls are not routed from mobile VoIP users when they are off-site, as the emergency services may arrive at the wrong location.

Another option is to have a single physical phone line or GSM SIP gateway attached to the IP phone system solely for routing emergency calls. All other calls would be routed to the normal SIP providers.

If it is not technically feasible to route calls to the emergency service number, it may be useful to provide a brief recorded message telling the user to call emergency services from another phone. After playing the message once or twice, the PBX should hang up, so the user knows that the call is not being routed.

In the early days of telephony, not every home or office had a telephone. In Britain, which is known for its distinctive red phone boxes, the police force took responsibility for installing many blue phone boxes for use by police and people without a telephone. Some people feel that it is important for the emergency services to be proactive again and ensure that emergency call centers have a presence on the Internet, accepting calls directly from users of SIP and XMPP.