Mobile Telephone Service
Encyclopedia
The Mobile Telephone Service (MTS) is a pre-cellular
VHF
radio system that links to the Public Switched Telephone Network
(PSTN). MTS was the radiotelephone equivalent of land dial phone service. , only rural
and wilderness areas were still using the system.
The Mobile Telephone Service was one of the earliest mobile telephone standards. It was operator assisted both directions, meaning that if you were called from a land line
the call would be routed to a mobile operator, who would route it to your phone. Similarly, to make an outbound call you had to go through the mobile operator, who would ask you for your mobile number and the number you were calling, and then would place the call.
This service originated with the Bell System
, and was first used in St. Louis
on June 17, 1946. The original equipment weighed 80 pounds, and there were initially only 3 channels for all the users in the metropolitan area, later more licenses were added bringing the total to 32 channels across 3 bands (See IMTS frequencies). This service was used at least into the 1980s in large portions of North America.
This protocol was replaced by Improved Mobile Telephone Service
(IMTS).
and Canada
. The channels are identified by pairs of letters taken from positions on a North America
n telephone
dial that, when changed to digits, form (for 12-channel mobile sets) 55, 57, 95 and 97.
and interference
since a radio closer to the terminal will sometimes take over the channel due to having a more powerful signal. The service uses technology that has been manufacturer discontinued for more than three decades.
The driver for replacement in most of North America, particularly large cities, was congestion, the inability of the network to carry more than two dozen channels in a geographic area. Cellular service resolved this congestion problem very effectively, especially since cellular frequencies, typically UHF, do not reach as far as VHF frequencies and can therefore be reused. The ability of a cellular system to use signal strength to choose channels and split cells into smaller units also helps expand channel capacity.
The driver for replacement in remote areas, however, is not network congestion, but obsolescence. Because the equipment is no longer manufactured, companies still using the service must struggle to keep their equipment operating, either by cannibalizing from retired equipment or improvising solutions. Due to insufficient traffic, cellular is not a cost-effective replacement. Currently, the only viable solution is satellite telephony
, as the small number of "base stations" orbit the planet serving large geographic regions as they pass over. Cost, however, has been an issue, and the replacement will become acceptable to VHF mobile customers gradually, as the cost of satellite telephony has been dropping and will continue to drop.
Many MTS frequencies
are now used for local paging services. They are only found in some parts of rural North America, having been replaced in most areas by cellular service in the 1980s or later.
The service territory of Northwestel
has only eliminated ten MTS locations since 2003; in the case of six sites, cellular is available and the company had to rent tower space for five sites, making them even more unprofitable; four other sites had near zero traffic. The remainder of the MTS network is still operating, though at a deficit, virtually blanketing the Yukon
and northern British Columbia
highway network, the western Great Slave Lake
region, the Mackenzie River
and the Mackenzie Delta. As noted above, cellular service is too costly to install in these areas due to a more limited signal reach, cellular sites are more complex technology, and they would still require the same logistical support, like electricity supplied from diesel generators, using barged-in fuel.
Outgoing calls were placed when the operator connected to a base station (originally using a cord board, but by the 1990s could be done by dialing a code sequence from a TOPS position), then announced the call over the channel (giving the channel's name first), e.g.,
The page would usually be repeated twice more after a pause. The called party had to have their unit on and the volume set at a level that allowed them to notice a call and then listen to the called number. If the called party heard an incoming call, they would then use the microphone to announce they were receiving the call, and the operator would allow the two parties to speak, monitoring for the end of the call and marking a manual ticket for billing.
The format of such "voice-called" mobile customer numbers varied by jurisdiction. B.C. Tel
, for example, used seven-character numbers starting with N or H, a digit (often 1), then five more digits for the individual customer. AGT
in Alberta used seven-character numbers.
Soon enough, customer equipment, "selective call", was developed that had a built-in circuit that could be programmed to recognize a five-digit code as its own, in a manner similar to IMTS systems and crude compared to cellular phones. The phone company would assign the customer a number and the customer would have it programmed into the set by the phone company or by a dealer.
The operator would connect to the base station by cord board and key the five-digit number; in the 1990s, phone operators at TOPS positions would key the five digits after dialing the code to initiate the call and then identify the base station; a typical TOPS operator code would consist of a two digit sequence for voice-call or selective call, a three digit sequence for the base station, then the customer number.
The base station would signal the five digit sequence; any and all radios tuned to that base station would detect the sequence and compare it with their own; if it matched, the unit would signal its user with a bell or buzzer, and the user could then answer and announce the identity of their unit, similar to how a voice-call user would respond.
Calls from mobile units to a base station were started by signaling the operator by pressing the microphone button. The operator would plug into the channel (automated TOPS systems routed the incoming call through the normal queue), announce availability and the channel name, and the customer would identify their mobile number. (Security systems were sometimes adopted later to prevent fraud, by the customer giving a confidential number. In an automated connection to the operator, other radios on the base station could hear the transmission from the station, not what the radio user was transmitting.) The customer would then specify the details of their call, either to another mobile or to a landline number, which the operator would then place. The call was manually ticketed prior to the use of TOPS, and automatically ticketed if the mobile user was automatically connected to the TOPS operator.
Very few companies automated MTS to use TOPS as most were able to discontinue MTS services due to the reasons above: they could not meet the service demand except by switching to cellular. Northwestel
was one company still offering MTS that tied the base stations into TOPS.
A variant of MTS used short-wave frequencies, and was known as High Frequency or High Frequency-Single Sideband, so named for using frequencies between 3 and 30 MHz. These services required far fewer base stations and were used to reach distant locations over vast territories. The drawback was that the frequencies were extremely noisy from various interference, and were subject to propagation problems due to time of day, mostly due to the sun's effect on the ionosphere. Northwestel, which discontinued the service shortly after 2000, could not tie this system into TOPS, and had to aurally monitor the channels using speakers to listen for incoming calls.
For billing purposes, many MTS base stations were identified with a very close-by rate center of an automatic exchange. However, if there was no nearby rate center, they became an "Other Place Point". Phone companies typically identified these, and single points such as an individual telephone in a rural area, using a six-digit combination of 88T-XXX, where T is a digit from 6 to 9, and X is any digit 0-9. For example, Fox Lake, Yukon Territory, was 889-949. This combination would serve the same purpose as the NANP area code and central office code, with its own latitudinal-longitudinal coordinates, to allow a distance to be calculated for rating of a call. This coding system, which was in its zenith of usage during the 1980s and 1990s, was rendered unusable when the North American Numbering Plan administrator withdrew the 88X codes for future use as toll free (e.g. 1-800-) services.
By the end of the 1990s, very few companies still had need of the Other Place Point codes, and other rating arrangements were made. For example, Northwestel would use the nearest exchange for calls to its mobile points from other phone companies, and would code the locations in its billing software for calls within the company's operating territory. The rate impact was negligible for calls over longer distances.
Cellular network
A cellular network is a radio network distributed over land areas called cells, each served by at least one fixed-location transceiver known as a cell site or base station. When joined together these cells provide radio coverage over a wide geographic area...
VHF
Very high frequency
Very high frequency is the radio frequency range from 30 MHz to 300 MHz. Frequencies immediately below VHF are denoted High frequency , and the next higher frequencies are known as Ultra high frequency...
radio system that links to the Public Switched Telephone Network
Public switched telephone network
The public switched telephone network is the network of the world's public circuit-switched telephone networks. It consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all inter-connected by...
(PSTN). MTS was the radiotelephone equivalent of land dial phone service. , only rural
Rural
Rural areas or the country or countryside are areas that are not urbanized, though when large areas are described, country towns and smaller cities will be included. They have a low population density, and typically much of the land is devoted to agriculture...
and wilderness areas were still using the system.
The Mobile Telephone Service was one of the earliest mobile telephone standards. It was operator assisted both directions, meaning that if you were called from a land line
Public switched telephone network
The public switched telephone network is the network of the world's public circuit-switched telephone networks. It consists of telephone lines, fiber optic cables, microwave transmission links, cellular networks, communications satellites, and undersea telephone cables, all inter-connected by...
the call would be routed to a mobile operator, who would route it to your phone. Similarly, to make an outbound call you had to go through the mobile operator, who would ask you for your mobile number and the number you were calling, and then would place the call.
This service originated with the Bell System
Bell System
The Bell System was the American Bell Telephone Company and then, subsequently, AT&T led system which provided telephone services to much of the United States and Canada from 1877 to 1984, at various times as a monopoly. In 1984, the company was broken up into separate companies, by a U.S...
, and was first used in St. Louis
St. Louis, Missouri
St. Louis is an independent city on the eastern border of Missouri, United States. With a population of 319,294, it was the 58th-largest U.S. city at the 2010 U.S. Census. The Greater St...
on June 17, 1946. The original equipment weighed 80 pounds, and there were initially only 3 channels for all the users in the metropolitan area, later more licenses were added bringing the total to 32 channels across 3 bands (See IMTS frequencies). This service was used at least into the 1980s in large portions of North America.
This protocol was replaced by Improved Mobile Telephone Service
Improved Mobile Telephone Service
The Improved Mobile Telephone Service is a "0G" pre-cellular VHF/UHF radio system that links to the PSTN. IMTS was the radiotelephone equivalent of land dial phone service...
(IMTS).
Channels
MTS uses 25 VHF radio channels in the United StatesUnited States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
and Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
. The channels are identified by pairs of letters taken from positions on a North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
n telephone
Telephone
The telephone , colloquially referred to as a phone, is a telecommunications device that transmits and receives sounds, usually the human voice. Telephones are a point-to-point communication system whose most basic function is to allow two people separated by large distances to talk to each other...
dial that, when changed to digits, form (for 12-channel mobile sets) 55, 57, 95 and 97.
| 12-Channel Mobile | | Ident | | 24-Channel Mobile | | Base Station MHz | |
|---|---|---|---|---|
| Transmit | Receive | |||
| JJ | 152.480 | 157.740 | ||
| XJ | 1 | 152.495 | 157.755 | |
| 1 | JL | 2 | 152.510 | 157.770 |
| XK | 3 | 152.525 | 157.785 | |
| 2 | YL | 4 | 152.540 | 157.800 |
| XL | 5 | 152.555 | 157.815 | |
| 3 | JP | 6 | 152.570 | 157.830 |
| XP | 7 | 152.585 | 157.845 | |
| 4 | JJ | 8 | 152.600 | 157.860 |
| XR | 9 | 152.615 | 157.875 | |
| 5 | YJ | 10 | 152.630 | 157.890 |
| XS | 11 | 152.645 | 157.905 | |
| 6 | YK | 12 | 152.660 | 157.920 |
| XT | 13 | 152.675 | 157.935 | |
| 7 | JS | 14 | 152.690 | 157.950 |
| XU | 15 | 152.705 | 157.965 | |
| 8 | YS | 16 | 152.720 | 157.980 |
| XV | 17 | 152.735 | 157.995 | |
| 9 | YR | 18 | 152.750 | 158.010 |
| XW | 19 | 152.765 | 158.025 | |
| 10 | JK | 20 | 152.780 | 158.040 |
| XX | 21 | 152.795 | 158.055 | |
| 11 | JR | 22 | 152.810 | 158.070 |
| XY | 23 | 152.825 | 158.085 | |
| 12 | JW | 24 | 152.840 | 158.999 |
Frequency problems and elimination of the service
These channels are prone to network congestionNetwork congestion
In data networking and queueing theory, network congestion occurs when a link or node is carrying so much data that its quality of service deteriorates. Typical effects include queueing delay, packet loss or the blocking of new connections...
and interference
Interference (communication)
In communications and electronics, especially in telecommunications, interference is anything which alters, modifies, or disrupts a signal as it travels along a channel between a source and a receiver. The term typically refers to the addition of unwanted signals to a useful signal...
since a radio closer to the terminal will sometimes take over the channel due to having a more powerful signal. The service uses technology that has been manufacturer discontinued for more than three decades.
The driver for replacement in most of North America, particularly large cities, was congestion, the inability of the network to carry more than two dozen channels in a geographic area. Cellular service resolved this congestion problem very effectively, especially since cellular frequencies, typically UHF, do not reach as far as VHF frequencies and can therefore be reused. The ability of a cellular system to use signal strength to choose channels and split cells into smaller units also helps expand channel capacity.
The driver for replacement in remote areas, however, is not network congestion, but obsolescence. Because the equipment is no longer manufactured, companies still using the service must struggle to keep their equipment operating, either by cannibalizing from retired equipment or improvising solutions. Due to insufficient traffic, cellular is not a cost-effective replacement. Currently, the only viable solution is satellite telephony
Satellite phone
A satellite telephone, satellite phone, or satphone is a type of mobile phone that connects to orbiting satellites instead of terrestrial cell sites...
, as the small number of "base stations" orbit the planet serving large geographic regions as they pass over. Cost, however, has been an issue, and the replacement will become acceptable to VHF mobile customers gradually, as the cost of satellite telephony has been dropping and will continue to drop.
Many MTS frequencies
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
are now used for local paging services. They are only found in some parts of rural North America, having been replaced in most areas by cellular service in the 1980s or later.
The service territory of Northwestel
Northwestel
Northwestel Inc. is the incumbent local exchange carrier and long distance carrier in Northern Canada. The company name is a portmanteau, sometimes spelled NorthwesTel, for Northwest Telecommunications.-Modern corporate history:...
has only eliminated ten MTS locations since 2003; in the case of six sites, cellular is available and the company had to rent tower space for five sites, making them even more unprofitable; four other sites had near zero traffic. The remainder of the MTS network is still operating, though at a deficit, virtually blanketing the Yukon
Yukon
Yukon is the westernmost and smallest of Canada's three federal territories. It was named after the Yukon River. The word Yukon means "Great River" in Gwich’in....
and northern British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
highway network, the western Great Slave Lake
Great Slave Lake
Great Slave Lake is the second-largest lake in the Northwest Territories of Canada , the deepest lake in North America at , and the ninth-largest lake in the world. It is long and wide. It covers an area of in the southern part of the territory. Its given volume ranges from to and up to ...
region, the Mackenzie River
Mackenzie River
The Mackenzie River is the largest river system in Canada. It flows through a vast, isolated region of forest and tundra entirely within the country's Northwest Territories, although its many tributaries reach into four other Canadian provinces and territories...
and the Mackenzie Delta. As noted above, cellular service is too costly to install in these areas due to a more limited signal reach, cellular sites are more complex technology, and they would still require the same logistical support, like electricity supplied from diesel generators, using barged-in fuel.
Operation
All calls were placed by a suitably equipped telephone operator.Outgoing calls were placed when the operator connected to a base station (originally using a cord board, but by the 1990s could be done by dialing a code sequence from a TOPS position), then announced the call over the channel (giving the channel's name first), e.g.,
- "Dawson Channel calling 2M-2368, 2M-2368, 2M-2368."
The page would usually be repeated twice more after a pause. The called party had to have their unit on and the volume set at a level that allowed them to notice a call and then listen to the called number. If the called party heard an incoming call, they would then use the microphone to announce they were receiving the call, and the operator would allow the two parties to speak, monitoring for the end of the call and marking a manual ticket for billing.
The format of such "voice-called" mobile customer numbers varied by jurisdiction. B.C. Tel
TELUS
Telus is a national telecommunications company in Canada that provides a wide range of telecommunications products and services including internet access, voice, entertainment, video, and satellite television. The company is based in Burnaby, British Columbia, part of Greater Vancouver...
, for example, used seven-character numbers starting with N or H, a digit (often 1), then five more digits for the individual customer. AGT
TELUS
Telus is a national telecommunications company in Canada that provides a wide range of telecommunications products and services including internet access, voice, entertainment, video, and satellite television. The company is based in Burnaby, British Columbia, part of Greater Vancouver...
in Alberta used seven-character numbers.
Soon enough, customer equipment, "selective call", was developed that had a built-in circuit that could be programmed to recognize a five-digit code as its own, in a manner similar to IMTS systems and crude compared to cellular phones. The phone company would assign the customer a number and the customer would have it programmed into the set by the phone company or by a dealer.
The operator would connect to the base station by cord board and key the five-digit number; in the 1990s, phone operators at TOPS positions would key the five digits after dialing the code to initiate the call and then identify the base station; a typical TOPS operator code would consist of a two digit sequence for voice-call or selective call, a three digit sequence for the base station, then the customer number.
The base station would signal the five digit sequence; any and all radios tuned to that base station would detect the sequence and compare it with their own; if it matched, the unit would signal its user with a bell or buzzer, and the user could then answer and announce the identity of their unit, similar to how a voice-call user would respond.
Calls from mobile units to a base station were started by signaling the operator by pressing the microphone button. The operator would plug into the channel (automated TOPS systems routed the incoming call through the normal queue), announce availability and the channel name, and the customer would identify their mobile number. (Security systems were sometimes adopted later to prevent fraud, by the customer giving a confidential number. In an automated connection to the operator, other radios on the base station could hear the transmission from the station, not what the radio user was transmitting.) The customer would then specify the details of their call, either to another mobile or to a landline number, which the operator would then place. The call was manually ticketed prior to the use of TOPS, and automatically ticketed if the mobile user was automatically connected to the TOPS operator.
Very few companies automated MTS to use TOPS as most were able to discontinue MTS services due to the reasons above: they could not meet the service demand except by switching to cellular. Northwestel
Northwestel
Northwestel Inc. is the incumbent local exchange carrier and long distance carrier in Northern Canada. The company name is a portmanteau, sometimes spelled NorthwesTel, for Northwest Telecommunications.-Modern corporate history:...
was one company still offering MTS that tied the base stations into TOPS.
A variant of MTS used short-wave frequencies, and was known as High Frequency or High Frequency-Single Sideband, so named for using frequencies between 3 and 30 MHz. These services required far fewer base stations and were used to reach distant locations over vast territories. The drawback was that the frequencies were extremely noisy from various interference, and were subject to propagation problems due to time of day, mostly due to the sun's effect on the ionosphere. Northwestel, which discontinued the service shortly after 2000, could not tie this system into TOPS, and had to aurally monitor the channels using speakers to listen for incoming calls.
For billing purposes, many MTS base stations were identified with a very close-by rate center of an automatic exchange. However, if there was no nearby rate center, they became an "Other Place Point". Phone companies typically identified these, and single points such as an individual telephone in a rural area, using a six-digit combination of 88T-XXX, where T is a digit from 6 to 9, and X is any digit 0-9. For example, Fox Lake, Yukon Territory, was 889-949. This combination would serve the same purpose as the NANP area code and central office code, with its own latitudinal-longitudinal coordinates, to allow a distance to be calculated for rating of a call. This coding system, which was in its zenith of usage during the 1980s and 1990s, was rendered unusable when the North American Numbering Plan administrator withdrew the 88X codes for future use as toll free (e.g. 1-800-) services.
By the end of the 1990s, very few companies still had need of the Other Place Point codes, and other rating arrangements were made. For example, Northwestel would use the nearest exchange for calls to its mobile points from other phone companies, and would code the locations in its billing software for calls within the company's operating territory. The rate impact was negligible for calls over longer distances.
See also
- Mobile radio telephone
- Mobile Telephone System
- Improved Mobile Telephone ServiceImproved Mobile Telephone ServiceThe Improved Mobile Telephone Service is a "0G" pre-cellular VHF/UHF radio system that links to the PSTN. IMTS was the radiotelephone equivalent of land dial phone service...
(IMTS)