Intermountain Gas Finds Solution for its Mobile Radio System
By Vaughn Entwistle, Zetron Inc.
Intermountain Gas is a retail distribution utility that supplies natural gas to the southern half of Idaho. In terms of square miles, Intermountain has one of the largest service territories of any distribution utility in the United States, due to Idaho`s large number of rural enclaves. Recently the utility completed the last phase of a two year program, building a unique Radio Access Control System (RACS)/LTR network to provide system-wide coverage for its mobile radio system (Figure 1).
In the beginning, the utility had a simple radio dispatch system that suffered from some major shortcomings. Bill Chapman, Intermountain Gas telecommunications manager, explains that these shortcomings were more than just an inconvenience: “We`re a natural gas distribution utility. We have to respond to after-hours calls because there`s always the potential of an emergency where someone could get hurt.”
Under the old system, when a customer called the utility`s office for service, the service order would be filled out and placed in a message box. Eventually, the service person would have to come into the office to pick up his messages, or messages would be dispatched to him in the field. If the service order was unclear, or the address was incorrect or missing, an additional delay was introduced. This was especially problematic when it came to after-hour calls because the field crews didn`t have a dispatcher to talk to.
The problem called for a way to remove this “filter” between customer and company. The first solution was Mobile-Tel; a system copied from the railroads that was really a half-duplex VHF mobile telephone. Mobile-Tel meant that a customer could call and speak directly with a service worker in the field.
“We put the system in using Zetron Model 45 Interconnects,” Chapman said. “It was such a success that I had managers coming to me to see how much it cost. When I told the figures, they would immediately tell me to put another one up, since we were saving more than that in two weeks by eliminating false callouts.”
LTR the Next Step
As a result of Mobile-Tel`s success, Chapman said that Intermountain`s two-way radio needs became increasingly telephonic in nature over the years. Then three years ago, the utility began planning for a new system. Each of Intermountain`s five major offices formed focus groups to study all the various systems offered by the major communications equipment suppliers.
“We looked at everything that was out there,” Chapman said. “We talked to all of the major vendors who were offering systems of this kind. While they were all really good, we found that, with some of the systems offered by major manufacturers, you needed to be bigger than we are in order to make it cost-effective.”
Centralized Processing a Drawback
A major design feature shared by many of the large manufacturers was centralized processing, which presented a problem for Intermountain Gas. “Centralized processing is fine if you own your own telephone company,” Chapman said, “or if you have miles and miles of microwave paths across your system and lots of vacant channels for the radio system to use. You can then put a computer at one central point where all of the signal processing takes place (in our case, Boise) and have towers all over the state that feed back to it. However, we use an entirely leased fiber-optic and microwave network; we don`t own and operate any of it. Because of this we wanted something where processing could be distributed. That`s why we eventually became interested in LTR, so that we would still have a local dispatch function, but the bulk of service for the system would be telephone” (Figure 2).
Chapman had another major reservation concerning the central processing approach: “It seemed very inefficient to us. We thought, why not have signal processing in each major city, so when the Pocatello service tech dials a Pocatello number the call never leaves the Pocatello system? This is exactly what Zetron brought to the table with RACS. Zetron`s RACS gives us the ability to build the thing in small enough units so we could put a Model 7032 RACS switch in every major location where the company`s customers are clustered, and then tie them together into a network using our in-place Lucent Technologies G-3 ECS system.”
An important factor in the utility`s choice was that LTR is an open protocol, which allows Intermountain Gas to buy radios from a number of different vendors. The RACS system could also integrate LTR systems with conventional UHF system systems in DTMF (Dual Tone Multiple Frequency) or select 5 signaling.
“Another thing that Zetron brought to the table that was very important to us was the varying signaling formats,” Chapman said. “Some of the competitive systems had very demanding signaling requirements. For example, we have some places where we use Multiplexed 56 kilobit channels that have to carry compressed voice and data. The Zetron signaling formats allowed us to use our in-place equipment to move the signals around. That made a big difference, cost-wise.” Western Communications, Boise, Idaho, performed the actual installation of the RACS, with assistance from Teton Communications in the Idaho Falls-Pocatello areas. Western is a special mobile radio and two-way sales and service provider.
Another advantage is that RACS features many advanced, telephone-style features including call forwarding, multi-party conferencing, roamer registration, dispatch group calling, voting, etc. Intermountain Gas is already making use of many of these.
“We use call forwarding, which works very well for our operations people,” Chapman said. “They may be in different vehicles from time to time. Because they have a CCID (caller ID) it`s very easy for them to forward their CCID to any vehicle they`re in. Also, with our construction and operations people, the horn honking feature is a virtual necessity, when you`ve got jackhammers going you have to do something to get their attention. We`re also using Roamer registration all the time, since there`s 30 or 40 of us who are regularly on the Interstate somewhere between the Oregon line and the Wyoming/Utah border.”
LTR Protocol Boosts Efficiency
But it is this first use of the LTR protocol over RACS that makes the Intermountain application particularly interesting.
“LTR allows more efficient use of the mountain top repeaters,” Chapman said. “It allows a repeater to share dispatch and dial tone (interconnect) functions. On every site, we reserve a channel for dispatch. If a site has five channels on it, we only allow four channels to be used for dial tone. On the fifth channel, dial tone is not available, so the dispatcher has an avenue to contact the units in the field if something goes wrong. If we allowed dial tone access to every channel, the dispatcher could be locked out, and that`s a chance we can`t take.”
Note: LTR is a registered trademark of E.F. Johnson Company
Vaughn Entwistle has 11 years of experience as a communications specialist in technical industries. He is the writer/editor of Zetron`s monthly marketing newsletter, the Advantage.
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