Everybody is familiar with 9-1-1 service, which allows you to easily contact emergency services from your home phone. But what about your cell? Emergencies can happen when you're away from home. And even while you're at home, more households are moving towards a single-line solution, replacing their landline phones with mobile.

The FCC requires all cellular carriers to put through all 9-1-1 calls, even when the phone does not have an active service contract. Individuals who have medical conditions may do well to carry an emergency cell phone, even if they do not use a cell phone on a regular basis. It is also an ideal solution for the elderly, who may be at risk while out and about. Keeping an emergency cell phone in the car's glove compartment, along with a portable charger, can help avert a disaster in case of a breakdown or accident in a remote area.

The so-called E911 (enhanced 911) service, mandated by the FCC, also requires carriers to implement a system that tells emergency dispatchers the location of the caller. This has been a part of landline emergency services for several years, and when you call 9-1-1 from your home phone, the dispatcher automatically knows your callback number and your fixed location. But on a mobile phone, there are some technological challenges. Fortunately, the cell phone companies stepped up to the plate and came up with a solution. In Phase I of the FCC mandate, carriers had to create a system that would tell dispatchers the cell phone number of the caller, as well as the location of the cell tower, which would provide at least an approximate geographic location. More sophisticated location detection technology uses GPS-enabled cell phones to determine the location of the caller in an emergency.

Phase II, scheduled to be fully implemented by the end of 2005, goes a step further by providing Automatic Location Identification (ALI), with precise latitude and longitude of the caller, to the emergency dispatcher. This capability has been incorporated into many newer cell phones, but there are still older cell phones still in use. If you plan to use your cell phone as an emergency backup, make sure you have a newer "location-sensitive" phone that is equipped to handle this service.

There is no charge for calling 9-1-1 from a cell phone; the E911 infrastructure is paid for with a small surcharge on normal cell phone services.