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Posted by on September 5, 2008, 10:37 am
wrote:
> That would have been an MTS unit, they were made by GE or Motorola,
> later when dials were added the were IMTS phone. The IMTS you could
> dial out like a regular phone and had dial tone. The olde MTS units you
> reached an operator. One of the GTE vehicles that I drove had one and
> it was very interesting since phone were very rare; just doctors and
> attorneys had them, maybe a few movie stars.
Could someone elaborate on the various generations of pre-cellular
mobile phone technology? That is, what was the difference between
"MTS" and "IMTS" of the 1960s, and when did they replace whatever Bell
originally came out with in 1948 for mobile phones?
At the same time Bell offered automobile mobile phones they installed
a few in premium railroad trains. Phones and trains shared the same
radio channels and based on the readings I think there were only two
channels available for use back then. Phones only worked in or near
cities.
I'm not sure when two-way car radios for police came out, but they
were enough of a novelty in 1948 that a fast response to a traffic
accident thanks to radio dispatching warranted a mention in the
newspaper.
Today many public safety units are converting to digital radios from
analog. However, there have been many newspaper reports of digital
radios failing in critical situations due to dead spots, apparently a
digital signal is harder to receive than the older analog signals.
I'm not sure what the advtg of digital over analog is in public safety
applications (saving bandwidth?). But one capabiltiy lacking today is
optional common channels between police, fire, and rescue which often
work on isolated networks. That is, a policeman can't communicate
with a fireman, rather, he has to relay messages through the
dispatchers. Apparently bringing city systems together is a tough
job, in New York City they're still working on it and there are many
challenges partly since the police system is a different technical
architecture than the fire system, and of course the systems must
remain in active use 24/7.
I can't help but wonder if the old Bell Labs of the Bell System was
still in full strength that R&D in this field, particularly in
applying a sound technology, the state of the art would be improved.
Bell Labs took time to develop new technology, but they tested the
heck out of everything in actual service and debugged it accordingly.
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Posted by Geoffrey Welsh on September 6, 2008, 12:30 am
hancock4@bbs.cpcn.com wrote:
> Today many public safety units are converting to digital radios from
> analog. However, there have been many newspaper reports of digital
> radios failing in critical situations due to dead spots, apparently a
> digital signal is harder to receive than the older analog signals.
I'm guessing that this has more to do with the frequencies typically used for
a given type of signal and not specifically analog vs. digital. The older
analog channels - which operated at lower frequencies - propagated better in
city environments than devices built to use recently-available higher
frequencies. I also believe that this is part of the reason why the
government wants some of the relatively low (by today's standards)
frequencies from analog television broadcasts for public safety use.
There may also be issues of capacity, where a sufficient number of responders
using all the different 'trunks' fill the available bandwidth.
> I'm not sure what the advtg of digital over analog is in public safety
> applications (saving bandwidth?). But one capabiltiy lacking today is
> optional common channels between police, fire, and rescue which often
> work on isolated networks. That is, a policeman can't communicate
> with a fireman, rather, he has to relay messages through the
> dispatchers.
Yes, they're looking for more bandwidth (or, more specifically, more virtual
channels in a digital stream than they could have fit frequency-based
physical channels in the band available before. And, yet, in retrospect it
seems obvious that having all these responders on different channels can be a
disadvantage when co-ordinating responses to larger events and potentially
dangerous if, say, firefighters can't tell ambulance attendants that a
building is about to collapse.
If I recall correctly, some of these devices have the ability to switch to
other services' channels, and perhaps some even have the ability to tap into
multiple (all?) channels simultaneously. This would be extremely useful in
the "get out, the building's coming down!" scenario.
> I can't help but wonder if the old Bell Labs of the Bell System was
> still in full strength that R&D in this field, particularly in
> applying a sound technology, the state of the art would be improved.
> Bell Labs took time to develop new technology, but they tested the
> heck out of everything in actual service and debugged it accordingly.
I believe that you hit the nail on the head in the latter half of that
paragraph: there's no shortage of bright people working on leading edge
technology but it feels like the results are often brought to market
half-baked, slapped together as quickly and as cheaply as possible with
little regard to quality, usability, versatility, durability, and a whole lot
of other descriptive words we wish we could use more often. Business
considerations, usually driven by the need for short term financial gains,
seem to dominate the technology development field.
--
Geoffrey Welsh <Geoffrey [dot] Welsh [at] bigfoot [dot] com>
.
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Posted by Ron Kritzman on September 6, 2008, 12:32 am
hancock4@bbs.cpcn.com wrote:
> Could someone elaborate on the various generations of pre-cellular
> mobile phone technology? That is, what was the difference between
> "MTS" and "IMTS" of the 1960s, and when did they replace whatever Bell
> originally came out with in 1948 for mobile phones?
In 1978 when I went to work for a large RCC in Chicago we still had a
manual mobile setup. Not even MTS. Just a 2 way radio system with
selective signaling. It was very 1960s, even in '78. Telco at the time
was using IMTS, if you could get one. The waiting list was long.
I had a trunk mounted 2 way radio with a handset with a push to talk
bar. The radio was full duplex but you still had to use the push-to-talk
on the to transmit. Some of us filed down one end if the PTT bar so we
could catch it under the metal escutcheon for push-on push-off operation.
We had several channels and customers were assigned to a particular
channel, but as an employee engaged in system maintenance I had multi
channel radio with all of them. When idle I would always have to return
to my home channel so that they could ring me.
Incoming calls were answered by operators who asked for the mobile unit
number. They would punch up the number on the tone box and wait for the
mobile to answer. Signaling was 2x2 tone. Two tones together, followed
by 2 more tones together. The decoder box, external to the radio, had 4
of the big old copper cased Vibrasponder reeds. There was no bell or
buzzer. When the tones were decoded the speaker would unmute and you
would hear the rest of the 2nd tone pair followed by a voice
announcement. "Chicago Seven Two Eight Two. Ron? You out there?" Lifting
the handset off the hook would re-mute the speaker so that you wouldn't
get feedback. When you answered, the mobile op would hit the connect
button which would take her out of the call and leave the mobile patched
to the caller. Calling out was manual as well. Lift the handset, make
sure no one is already using the channel, key the transmitter and give
your unit number. When the operator answered you'd give them the number
to dial. Customers usually had cards on file so that they could just ask
for their office or residence.
Privacy was nil. Other mobiles could and and did listen in, as could any
2-way radio enthusiast or kid with a scanner. The speakers were always
on in the radio room so the operators could tell when a he call was
ended. To this day it amazes me what manner of indiscretions crossed
those wide open channels.
- Ron
--
remove the letters in caps to reply
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Posted by T on September 6, 2008, 5:33 pm
ron@dbONAYAMSPAYmasters.com says...
> hancock4@bbs.cpcn.com wrote:
>
> > Could someone elaborate on the various generations of pre-cellular
> > mobile phone technology? That is, what was the difference between
> > "MTS" and "IMTS" of the 1960s, and when did they replace whatever Bell
> > originally came out with in 1948 for mobile phones?
>
> In 1978 when I went to work for a large RCC in Chicago we still had a
> manual mobile setup. Not even MTS. Just a 2 way radio system with
> selective signaling. It was very 1960s, even in '78. Telco at the time
> was using IMTS, if you could get one. The waiting list was long.
>
> I had a trunk mounted 2 way radio with a handset with a push to talk
> bar. The radio was full duplex but you still had to use the push-to-talk
> on the to transmit. Some of us filed down one end if the PTT bar so we
> could catch it under the metal escutcheon for push-on push-off operation.
>
> We had several channels and customers were assigned to a particular
> channel, but as an employee engaged in system maintenance I had multi
> channel radio with all of them. When idle I would always have to return
> to my home channel so that they could ring me.
>
> Incoming calls were answered by operators who asked for the mobile unit
> number. They would punch up the number on the tone box and wait for the
> mobile to answer. Signaling was 2x2 tone. Two tones together, followed
> by 2 more tones together. The decoder box, external to the radio, had 4
> of the big old copper cased Vibrasponder reeds. There was no bell or
> buzzer. When the tones were decoded the speaker would unmute and you
> would hear the rest of the 2nd tone pair followed by a voice
> announcement. "Chicago Seven Two Eight Two. Ron? You out there?" Lifting
> the handset off the hook would re-mute the speaker so that you wouldn't
> get feedback. When you answered, the mobile op would hit the connect
> button which would take her out of the call and leave the mobile patched
> to the caller. Calling out was manual as well. Lift the handset, make
> sure no one is already using the channel, key the transmitter and give
> your unit number. When the operator answered you'd give them the number
> to dial. Customers usually had cards on file so that they could just ask
> for their office or residence.
>
> Privacy was nil. Other mobiles could and and did listen in, as could any
> 2-way radio enthusiast or kid with a scanner. The speakers were always
> on in the radio room so the operators could tell when a he call was
> ended. To this day it amazes me what manner of indiscretions crossed
> those wide open channels.
And even when cellular moved into AMPS an Alinco DJ580T was very
capabable of listening in to the 800MHz band where the cell phones
lived.
Then of course if you were fortunate enough to have a Radio Shack
computer controlled scanner of a certain vintage you could also buy a
package that would allow you to follow calls from cell site to cell
site. Friend of mine managed to get the law enforcement version of it.
Nothing is ever secure.
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Posted by Steven Lichter on September 6, 2008, 12:34 am
hancock4@bbs.cpcn.com wrote:
> wrote:
>> That would have been an MTS unit, they were made by GE or Motorola,
>> later when dials were added the were IMTS phone. The IMTS you could
>> dial out like a regular phone and had dial tone. The olde MTS units you
>> reached an operator. One of the GTE vehicles that I drove had one and
>> it was very interesting since phone were very rare; just doctors and
>> attorneys had them, maybe a few movie stars.
>
> Could someone elaborate on the various generations of pre-cellular
> mobile phone technology? That is, what was the difference between
> "MTS" and "IMTS" of the 1960s, and when did they replace whatever Bell
> originally came out with in 1948 for mobile phones?
>
> At the same time Bell offered automobile mobile phones they installed
> a few in premium railroad trains. Phones and trains shared the same
> radio channels and based on the readings I think there were only two
> channels available for use back then. Phones only worked in or near
> cities.
>
> I'm not sure when two-way car radios for police came out, but they
> were enough of a novelty in 1948 that a fast response to a traffic
> accident thanks to radio dispatching warranted a mention in the
> newspaper.
>
> Today many public safety units are converting to digital radios from
> analog. However, there have been many newspaper reports of digital
> radios failing in critical situations due to dead spots, apparently a
> digital signal is harder to receive than the older analog signals.
>
> I'm not sure what the advtg of digital over analog is in public safety
> applications (saving bandwidth?). But one capabiltiy lacking today is
> optional common channels between police, fire, and rescue which often
> work on isolated networks. That is, a policeman can't communicate
> with a fireman, rather, he has to relay messages through the
> dispatchers. Apparently bringing city systems together is a tough
> job, in New York City they're still working on it and there are many
> challenges partly since the police system is a different technical
> architecture than the fire system, and of course the systems must
> remain in active use 24/7.
>
> I can't help but wonder if the old Bell Labs of the Bell System was
> still in full strength that R&D in this field, particularly in
> applying a sound technology, the state of the art would be improved.
> Bell Labs took time to develop new technology, but they tested the
> heck out of everything in actual service and debugged it accordingly.
>
I believe an MTS unit would require you to pick the phone up and push a
button to reach an operator. The IMTS (Improved Mobile Telephone
Service) would have a dial and later Touch Tone, you would pick a
channel or it would search and then you would get dial tone and it would
be just like a regular wired phone. There were problems when you moved
from one area to another because the towers were located on hills or on
top of buildings, so if something was blocking it you would get no
service, plus I seem to remember that if you were in another service
area you would have to go through an operator. It has been 12 years
since I have even seen one other then in the moved or a picture online.
--
The Only Good Spammer is a Dead one!! Have you hunted one down today?
(c) 2008 I Kill Spammers, Inc. A Rot In Hell Co.
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> later when dials were added the were IMTS phone. The IMTS you could
> dial out like a regular phone and had dial tone. The olde MTS units you
> reached an operator. One of the GTE vehicles that I drove had one and
> it was very interesting since phone were very rare; just doctors and
> attorneys had them, maybe a few movie stars.