NOVA SCOTIA INTEGRATED MOBILE
RADIO SYSTEM (NSIMRS)
The Historical View
Last updated
Oct 4 2021
The initials NSIMRS are commonly
pronounced as an acronym "nizmirz" or "nismirs", and in this page the
assumption in syntax is that
you will be pronouncing it as a word, without "the" preceding it.
This page and the linked pages associated with it refer to
NSIMRS as it existed and functioned in the 1980's and 1990's.
It was replaced by the first NS trunk system in and around the year 2000.
Some components of NSIMRS still exist today, and along
with other components added, the term NSIMRS is still used. This
page is NOT about the modern NSIMRS.
NSIMRS was a set of VHF repeater
sites operated by the province of Nova Scotia and located throughout the
province, and in full operation throughout the 1980's and 1990's. It
provided the radio communications infrastructure required by mobile units
belonging to the province, and as well by associated public service agencies,
including the ambulance service and volunteer fire departments and other
volunteer services such as ground search and rescue and emergency measures
management. It was intended for joint use by the province, the RCMP, local
police, EMO, GSAR and fire departments. This system was substantially
reduced when the first trunked mobile radio system came into service in and
around the year 2000. Most of the networks on NSIMRS were
decommissioned and equipment removed soon after the changeover. All
of the tower sites in NSIMRS still exist today but with a much different
capability than what is described here.
The system was originally made up of
24 provincially owned repeater sites, as shown on this
map. Eight additional sites were added
over time to meet the specific needs of the Department of Transportation
("highways"). The individual sites were linked by a microwave system so
that any site could be connected with any other, as described father down this
page.
On the map the lines shown are the routes of the microwave system that linked
the sites between each other and back to Shubie Radio, RCMP Telecoms, and to
certain central offices and hospitals.
H Division of the RCMP had repeaters on all or almost all of the NSIMRS
towers, so can be regarded as a
lodger user, but they also had many other repeaters throughout the province.
NSIMRS was made up of six specialized networks. Specific pages with frequency and tone information plus in some cases maps are linked from here. the "frequency range" is the approximation of the set of specific frequencies used on the outputs of the repeaters. Inputs were at various offsets. Note that the RCMP's old network is linked here as a convenience, but it was not actually part of NSIMRS, but rather a compatible lodger at many sites, but with many other sites not at NSIMRS locations. Note that in 2023 I hope to add maps for some of the components currently without them. I have never seen a map for the Municipal Police Network but my understanding is that their repeaters were located only in areas in which there were municipal forces (not including the Halifax-Dartmouth area), with the purpose of allowing communications between them and with the RCMP.
The system maps referenced in the table below are those that were carried by mobile users to help them determine which channel to turn to in different parts of the province, as this had to be manually selected.
Network/Department | Frequency Range | Description Link | System Map Link |
Natural Resources | 163 MHz | DNR | |
Transportation | 150 MHz | DOT | |
Hospital/Ambulance | 159 MHz | Ambulance/Hospital | Map is with description |
General Govt Services | 143 MHz | EMO/GSS | Map |
Provincial Fire Grid (VFD) | 152 MHz | Fire Grid | Fire Grid Map |
Municipal Police | 153.59 MHz | Municipal Police | |
RCMP | 155 MHz | RCMP |
This chart lists the twenty-four sites plus eight additional sites used originally only by the Department of Transportation. Repeater output frequencies are shown for five of the networks. Specific pages linked above have more detail. The Municipal Police Network, not shown here, had only one frequency (153.59 MHz). Additionally the RCMP was a lodger user of the network, and used several other sites in addition to the those listed.
Site # | Rptr Site | Area Served |
1 | Middle Ohio | Shelburne |
2 | East Kemptville | Yarmouth |
3 | North Range Corner | Digby County |
4 | DND | Annapolis |
5 | Springfield | Springfield |
6 | Garland | Kings County |
7 | Liverpool | Queens County |
8 | Sherwood | Lunenburg County |
9 | Willow Hill | West Hants |
10 | Hammonds Plains | Halifax |
11 | Jerusalem Hill | Musquodoboit Hbr |
12 | Marinette | Sheet Harbour |
13 | Kirkhill | Parrsboro |
14 | Sugarloaf | Cumberland County |
15 | Nuttby Mtn | Colchester County |
16 | McLellan's Mtn | New Glasgow |
17 | Cochrane Hill | Sherbrooke |
18 | Fairmont | Antigonish |
19 | Lundy | Guysborough |
20 | Oban | St. Peter's |
21 | Rear Boisdale | Sydney |
22 | Kiltarlity Mtn | Inverness County |
23 | Cape Smokey | Ingonish |
24 | Money Point | Cape North |
? | Shubie | Milford DOT shed |
? | Hammonds Plains? | Sackville DOT shed |
? | Italy Cross RCMP | Bridgewater area sheds |
? | Barr Settlement | Noel DOT shed |
? | Salem | Amherst shed |
? | Savannah (French Lake) | Pubnico area shed |
? | Creignish | Port Hastings area shed |
? | Hunter's Mtn | Baddeck area shed |
Note that the sites
appearing without site numbers are extra sites or frequencies
on existing sites, that were added to serve only the Dept of Transportation, due
mostly to radio traffic congestion in the winter months, with the need to
establish separate
radio channels.
The users of any one network could access directly only that one network. They could use the local repeater in the normal way, but if suitably equipped with tone-signalling equipment, could dial up distant repeaters in their own network from one end of the province to the other. Distant repeaters were called up by dialing the specific repeater number. For example a DNR mobile unit in the Halifax area could access the local repeater at Hammonds Plains and then dial 221 to access the Sydney area (200 for DNR plus 21 for the Rear Boisdale repeater). It is unknown what numbers were used for the extra DOT repeater sites. Additionally there were offices equipped with tone-accessed radios, so that field units could call the head office, or ambulances could call hospitals. The mobile would dial them just as if they were dialing a distant repeater, and the base units would have numbers made up of the network prefix and then a number from 25 upwards. For example a central office for DNR had the number 225. These base units would not have to constantly monitor their local frequency, but rather could answer when signaled specifically.
Connection between networks (patching) was possible through Shubie Radio, the central control centre for the system, operated at that time by the Department of Natural Resources. Any unit with tone signal equipment could dial 0 to contact the Shubie operator and if desired request a patch to another network. This was not something heard often, but occasionally ambulances, rural fire trucks, vehicle compliance officers, and RCMP units could be heard patched to other networks. Shubie Radio also provided a dispatch and information service for users, and patches to the landline telephone system.
The lodger RCMP network could also be linked to components of NSIMRS by way of a link that would be established between Shubie Radio and RCMP Telecoms.
The IMRS began to be phased out in 2000 with the advent of the Nova Scotia Trunked Mobile Radio System. For several years many of the repeaters stayed in place, as of course it took time and money to remove the equipment. By at least 2004 the DNR and Ambulance networks were completely gone. The Fire Grid remains in service as in many cases it is used for dispatching rural departments or for their operations. Similarly the General Service network, which is now referred to as the EMO network remains available for volunteer use and as an emergency backup to the trunk system.