If you work in an office, your work days include the standard routine of commuting to work and taking your place at a cubicle in a corporate facility amid your fellow employees.
Most likely, your employer has provided you with a desk and a laptop, and on your desk is a telephone connected to the corporate multi-line telephone system (MLTS) known as an MLTS/PBX. Alice in accounting or David in sales is easily reached by directly dialing that person's extension number. Reaching someone outside of your company is just as easy. First, an access code is dialed, then the 10- or 11-digit telephone number of the desired remote party. The rest is telephone network magic that is likely out of sight and out of mind.
Nugget 1 — Dial plans
A fact that is not often considered: Much like an IP addresses, public telephone numbers must be left-unique. That means you cannot have an internal extension number of 1201 appear in the system because it would conflict with any public number that starts with 1201, such as the Bergen County Law and Public Safety Institute at 1-201-785-5700, for example.
Given this hard fast rule, how can any MLTS/PBX resolve this problem while still maintaining left-uniqueness in the dial plan? Here is where the access code comes into play. Utilizing an 8, a 9 or some other digit signals the MLTS/PBX that the additional digits that follow should be treated as external numbers.
+ Also on Network World: Why cellular 911 has location problems +
While the access code—let’s assume we have used a 9—was used to maintain the logic of a left-unique phone number segregating internal and external calls, we have created some additional constraints to be dealt with.
First and foremost, the digit 9 now has a single purpose. Because no other dialing patterns—internal or external—can begin with this number, any extension range starting with 9 cannot exist.
More problematic is the direct dialing of 911, which also could not exist. It is for this reason that some have suggested changing the access code to an 8 or a 7, but that could bring on even more dial plan problems. Fortunately, new ways have been developed in MLTS/PBX systems that allow for dial plans that are not left-unique. More on that in a bit, as we still need some additional background on the fundamentals.
By the way, congratulations! You have just learned the fundamental basics of dial plan design and are ready to tackle the larger challenges around getting your telephone system programmed to dial 911 efficiently in the event of an emergency.
Who controls 911?
The FCC relies on organizations such as the National Emergency Number Association (NENA) and the Association of Public Safety Communications Officials (APCO International), to act as standards bodies for the public safety community. They operate under the premise of 911 anywhere, anytime and on any device. In addition to promoting the efficient policies for 911, they introduce legislation as needed.
One thing you’ll notice on the side of any police car, fire truck or EMS vehicle is a phrase saying, “In case of Emergency – Dial 911,” or “For Police Fire or Medical – Dial 911.” I have never seen a public agency add a tagline to that message that says “Unless you are using a phone on an MLTS/PBX, then dial 9-911.” This requirement is the tragic reason why Kari Hunt died after an attack in a hotel room in Marshall, Texas, in December 2013. Hunt's 9-year-old daughter knew what to do; she was instructed about 911 many times. Yet the girl's four calls to 911 from within the hotel room in which her mother was stabbed never went through because the extra 9 was needed.
Nugget 2 — The dial plan fix
Barely 600 words into this article, and look what an expert you have become! You now know the history and the reasons behind the problem, and now you're about to learn the efficient fix for it.
As enterprise voice networks became more complex and inter-office dialing expanded to local multi-building campus connectivity, as well as connectivity across the globe, dial plans became more complicated. Most PBX manufacturers developed various software enhancements that resolved phone number left-unique requirements.
A simple interdigit timer, which would wait between digits, was introduced. When that timer expired, the numbers, as collected, would be processed. With this new logic, extension 1201 could now co-exist with extension 12017 and external phone number, 1-201-785-5700. Additionally, the digits 911 would no longer conflict with any internal or external number. The only downside is a slight pause when dialing numbers not left-unique.
Nugget 3 — On-site notification (OSN)
With access to 911 now optimized in the system, OSN improves the challenge of caller location. With 911 networks based on Caller ID for routing to the right agency as well as providing the location information, each station in a building requires a unique Caller ID to communicate precise location details to the 911 center, a prospect often financially unsustainable by many businesses.
OSN can provide notification when and where an MLTS 911 call event occurs. When public safety arrives, they are expected, and assistance can be offered that directs them to where they are needed. This simple fix also minimizes the cost of managing the Automatic Location Database, unless buildings are added or moved.
Nugget 4 — If it's broken, get it fixed (free)!
If you buy a ticket to the latest box office hit movie and they only show you a preview, you are likely to demand a refund. The same should apply to an MLTS/PBX. If you purchase of a new system (or pay monthly maintenance for a system) and you have to pay extra to be able to dial 911 directly (or to need to do or add something that allows 911 to work properly), wouldn't you consider the system broken? If your vendor refused to correct the issue, wouldn't that be a breach of their contract? Based on liability alone, most vendors will come out free of charge and turn on the basics.
Nugget 5 — Education counts; learn the basics
Class dismissed. You now have appropriate talking points enabling you to have an intelligent discussion with your service provider. Many agree Kari's Law will become law in 2016. It is already through the U.S. House of Representatives and is headed for the Senate. (It's already a state law in Texas.)
While there are multiple ways enterprise 911 can be addressed, the cost varies widely, and you need to be able to have an intelligent discussion to sort the wheat from the chaff. There are many new terms, and quite often you can waste a limited budget on something that is likely not the best fix.
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