VOIP phones are strange creatures to the phone system. Most people use VOIP phones as land-lines. The phone is plugged into a home computer or home network which is connected to the internet. For most VOIP users, there is no difference between their cool new internet-connected phone and their old land-line phone. For the 9-1-1 system, the difference is huge!
Land-lines are connected to a strictly controlled MSAG database. It’s 99% accurate and we almost definitely know where a land-line call is coming from. VOIP phones do not use the MSAG database. Emergency address information for VOIP phones are usually entered and updated by the subscriber. For example:
A guy in San Diego, California gets a VOIP phone. In order for 9-1-1 to work on his cool, new phone, he needs to give his address to the VOIP company or enter it into the VOIP program. One day, guy moves to Dallas, Texas. During all the hustle of moving, guy doesn’t update his emergency information for his VOIP phone. One day he has to call 9-1-1. Since he didn’t change his information his 9-1-1 call in Dallas gets routed to San Diego!
When The Dispatcher Answers the Phone…
This is the information we receive:
- Phone number that is placing the call
- Class of phone (VOIP)
- Subscriber name
- Address (This is the address given by the subscriber.)
- VOIP Company
This is what we see on our map:
If you’ve been following my posts in the last week, this image should look familiar. It looks exactly like a land-line call!
Conclusion
As with all emergency calls, the dispatcher is going to ask you to verify your location. Land-line calls have a small probability of sending the wrong information. Cell phones can have some problems sending the right information for a caller. However, VOIP is the one technology that can cause the biggest location mistakes. People who use VOIP in place of land-lines need to make sure their emergency information is accurate before they need to call 9-1-1.
Resources
Let’s say you’re in a situation where you’re injured, someone else is injured, there is a good chance of someone getting injured or someone is trying to injure or kill someone else. You’ve successfully found yourself in an emergency! So what do you do? You call 9-1-1.
If the phone you use to call 9-1-1 is plugged into a wall with a phone cord, you’re using a land-line. I’ll explain it a little more for those under 25 years old: If the phone your using doesn’t text, surf the internet, play music or play games, you’re probably using a land-line.
93% of the counties in the country operate E9-1-1 or Enhanced 9-1-1 service. So when you call 9-1-1 from a land-line phone, here’s what’s most likely going to happen:
Your call goes to a special 9-1-1 switch which then gets subscriber and location information for your phone number from the MSAG (Master Street Address Guide). Then your call, along with the data from the MSAG go to the PSAP (Public Safety Answering Point) that your address lists to.
When The Dispatcher Answers the Phone…
This is the information we receive:
- Phone number that is placing the call
- Class of phone (Residential, Business, Switchboard, Payphone, etc.)
- Subscriber name
- Address
- Telephone Company
This is great! Before anyone says a word we know, with 99% accuracy, your phone number, your address, and the name of the household or business you’re calling from. We’re still going to ask you for your location, your name and your phone number though because 99% accuracy is not 100% accuracy.
This is what we see on our map:
That red phone shows us what address you’re calling from. Some of the information I mentioned above is shown in this program. The rest of the information goes to another program.
Conclusion
If you call 9-1-1 from a land-line telephone we will more than likely know where you’re calling from. We’re still going to ask you where you are because as someone who works at a desk with 5 computers attached to it, we have a healthy mistrust of technology.
Up Next: What happens when I call 9-1-1 from a cell phone?
Resources
Since I have a month off between semesters at school, I’ve volunteered to help my co-workers understand the information we receive on our maps when a 9-1-1 call is made. But then I thought, why not help everyone understand what happens when you call 9-1-1?
What is 9-1-1 and how did it start?
I don’t really feel like I’m giving good educational value unless I throw some in some history. In 1957, the National Association of Fire Chiefs recommended use of a single number for reporting fires. Then in …..zzzzzzzzzzzzzzzzz… If you want to know the history of 9-1-1, go here1. I’m not going bore you with a history lesson if you don’t want it.
What are the different ways dispatchers received 9-1-1 calls?
The information automatically received by the dispatcher depends on what kind of phone is used to call in…
- Land Line: This is a phone that’s plugged into a wall that’s plugged into the phone system.
- Phase 1 Cell Phone: A cell phone that provides the dispatcher with the telephone number and carrier of the originator of a wireless 911 call and the location of the cell site or base station transmitting the call2.
- Phase 2 Cell Phone: A cell phone that provides all the information that a Phase 1 cell phone provides plus a more precise location specifically, the latitude and longitude of the caller. This information is accurate to within 50 to 300 meters2.
- VOIP: Stands for Voice-Over-Internet-Protocol. This is a fancy way of saying “Using your computer as a phone and the internet as the phone system.”
If you’re still a little confused, don’t worry. We’re going to go over this stuff in much more detail in later posts.
Glossary
I’m including a glossary in the introduction post because becoming familiar with the terms now will help you read the following posts. I am going to try really hard to make this as non-technical as possible, but I’m willing to face the idea that I may fail spectacularly at that.
- MSAG - Master Street Address Guide: Are you a conspiracy theorist who believes there’s a company based in Longmont, Colorado that has a giant database that links almost every land line telephone number to a subscriber, an address and a detailed description of the location of that address? If so, congratulations! You’re right! The MSAG database is how dispatchers know where you’re calling from when you call from a land line.
- PSAP – Public Safety Answering Point: This is the catch-all term for the place where 911 dispatchers receive your call. A PSAP can either belong to a city, county or state-wide entity. There are also regional PSAPs that dispatch for multiple agencies. The important thing to remember is that these are where your 911 call goes.
- Trilateration – Finding the distance between 3 different points to figure out your own location. GPS devices use satellites as their points. Network based phones use cell phone towers as their points. For a visual example, check out this site3.
Up Next: What happens when I call 9-1-1 from a land-line?
Resources
- http://www.nena.org/911-overview-facts
- http://www.fcc.gov/cgb/consumerfacts/wireless911srvc.html
- http://electronics.howstuffworks.com/gadgets/travel/gps1.htm
Scott Pantall | December 28, 2009
