Implementing SMS for 911 is not simple. First of all, many 911 call centers (PSAPs) still use analog equipment [1] For those PSAPs that do have NG911 equipment

Implementing SMS for 911 is not simple. First of all, many 911 call centers (PSAPs) still use analog equipment [1] For those PSAPs that do have NG911 equipment, managing an SMS "call" is tricky because SMS messages are not sent on a persistent connection. Each message requires routing through the wireless network to a selective router which then routes the call to a PSAP, and the PSAP routes the message to a call taker. So somehow subsequent messages need to be able to find their way to the same call taker that handled the first message. - How do all of the routing points know what "call" each message belongs to? - How do they know when the call ends? - What happens when the caller's location changes and the wireless network routes through a new selective router? - What if a PSAP is busy or offline? Unlike normal SMS, messages need to be re-routed. - 911 calls need to be recorded. Who is responsible for storing the SMS conversations? Sometimes PSAPs are required by a state to record conversations. If the SMS solution is a web-hosted application, state laws may need amending to allow the application provider to record the SMS conversation. The wireless network, selective router, and PSAP equipment may each be managed by a different entity, so it requires new laws, standards and equipment to coordinate a 911 SMS conversation correctly compared to normal SMS calls where the number that is being sent to maps to a single subscriber. [1] http://www.911.gov/ng911_law/whatisng911.html http://www.911.gov/ng911_law/whatisng911.html