“911, what is the location of your emergency?”


Our dispatchers working in the communications center.

In the 9-1-1 and emergency response business your location is the most important piece of information we need in order to deliver the appropriate response. This article is meant to provide a glimpse into the capabilities of current 9-1-1 technology and what may be to come in the next few years.

The City of Mountain View’s Emergency Communications Center (ECC) has been accepting and processing wireless and Internet-based “Voice over Internet Protocol” (VoIP) calls to 9-1-1 since 2004 and was amongst the first agencies in the Bay Area to do so. Today, well over half of the incoming calls to 9-1-1 in Mountain View are from mobile phones. The most important point of this article is that 9-1-1 service and technology, in this increasingly un-wired world, can be challenging when it comes to pinpointing the location from which the 9-1-1 call is coming. This is especially true when the caller is using a mobile phone.

Prior to the explosion of mobile and Internet-based communication technologies, when 9-1-1 was only available via “landline” telephone service, the address of the home or business associated with your phone number provided us with your street address. Since in most cases, your home or office building didn’t move around too much, we could usually rely on this address and — even if you could not tell us what the emergency was we were able to dispatch police, fire and/or Emergency Medical Services (EMS) to your address.

[…] in this increasingly un-wired world, can be challenging when it comes to pinpointing the location from which the 9-1-1 call is coming.

As the public has fully embraced mobile and Internet-based telephone services, we can no longer rely on a pair of wires that run from the telephone company’s central office to your home or business — you are “unwired” and able to dial 9-1-1 from your mobile phone, or your Internet-connected device, from wherever you may be. This has led to significant technical challenges both for the mobile phone carriers, mobile phone manufacturers, as well as for the 9-1-1 community and the telephone companies that serve us.

The Federal Communications Commission (FCC) and the telecommunications industry, along with 9-1-1 professionals, are working towards improving the ability for us to reliably determine your location when you dial 9-1-1, but there are a few limitations everyone should be aware of:

  • Many, but not all, wireless 9-1-1 calls are routed to the Mountain View ECC. Those wireless towers close to, or that provide coverage to freeways, are sometimes routed to the California Highway Patrol 9-1-1 Center for the Bay Area, which is located in Vallejo.
  • We will always ask you, at the beginning of a 9-1-1 call, “What is the location of the emergency?” While we realize that not everyone knows their precise address or intersection during every waking moment, it is ideal if you can articulate the approximate location of the emergency. If you don’t know, be clear with the 9-1-1 dispatcher and say, “I’m not sure of my exact location, but it is near [provide landmark, or license plate of a parked vehicle in a driveway].”
  • We also maintain many “common place” names in our systems, like Rengstorff Park or the library.

For our business community specifically, business phone systems, sometimes referred to as “PBX” systems, are widely available for businesses of all sizes. Unfortunately, if you as a business owner or manager are not aware of your PBX system’s 9-1-1 dialing capabilities (or limitations), we may not receive accurate address/location information from your premises when 9-1-1 is dialed by an employee. It is incumbent for all businesses that rely on on-premise or “hosted” business telephone systems to understand what happens when 9-1-1 is dialed, and (most importantly) that the proper address is being presented to the 9-1-1 call answering center.


If your business is larger, or spread amongst multiple buildings, or several floors of a building, it is essential that your phone system present the proper address and if possible, the suite, building, or floor information. Ask your phone system vendor or provider how 9-1-1 calls are handled and what “ALI” (Automatic Location Information) is presented to the local 9-1-1 center during an emergency. This is especially important if your phone system provides “mobility” in which employees can move their business phone from place to place or building to building or even possibly to their homes when telecommuting!  The California PUC has created an informative brochure which is available here.

Various options are being pursued by the mobile industry and several start-ups, some here in Silicon Valley, are working towards technologies that will make telephone handset location determination much more accurate, even (possibly) when indoors. The FCC is considering the possibility of tightening the requirements placed on the wireless carriers, as far as the accuracy of their 9-1-1 location.

Bottom line: 9-1-1 technology is progressing, but these are just a few of the basics it’s important for everyone to understand. While we hope you never have to dial 9-1-1 it’s always good to be aware of how it works and its use by law enforcement and other public safety entities.

KinerDoug Kiner is a Senior Systems Specialist with the City of Mountain View’s Public Safety Department. Doug has been with the City for over 20 years and works exclusively with the 9-1-1 and emergency response technologies used by our City.

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