1965 mobile phone on "Get Smart" [telecom]

We've previously talked about the phones used on the 1960s spy-spoof TV show "Get Smart".

The show is now available on DVD and I treated myself to a copy.

In a 1965 episode, Max uses a car's cigarette lighter to make a phone call. He then uses the car's mobile phone to light his cigarette.

I took a minute to look at the mobile phone unit. It did not have a dial, but appeared to be capable of having one. It had a Bell System logo in the center.

Was this the advanced mobile system in use until cell phones came out?

There were two rows of buttons, one row had 11 eleven gray buttons (couldn't make out the labels). the other row had four buttons of different colors.

Were the 11 buttons various channels the caller could choose from to make his call?

A friend of mine worked as a driver for a big shot in the 1970s, the car had a mobile phone in it. My friend said it was used just like a regular phone--to call him I would dial the regular seven digit number, and he would dial out. Did users have dial tones or have to press Send as we do today? We had to keep calls short as it was expensive.

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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.

Reply to
Steven Lichter

snipped-for-privacy@bbs.cpcn.com schrieb:

It was probably an IMTS phone, a system introduced in the 60s and not replaced until AMPS was introduced in 1983. It was the first US mobile phone system to offer direct dialling, the earlier MTS system was operator assisted only. To place a mobile originating call, the mobile phone would first request a dial tone from the mobile tower and digits were transmitted pulse-encoded over the already established voice channel as dialled, making it unecessary to press a "send" button after the number had been dialled.

Switching between different mobile towers was however not automatic and had to be manually initiated by the mobile phone user.


Reply to
Tor-Einar Jarnbjo

I had one! People would ask "How the hell does a kid in his 20s rate a phone in his car?" The real answer? I worked for an RCC. :-)

Reply to
Ron Kritzman

And, during the winter of '70, my biker landlord, who had a starter generator in the back of his pickup and used the phone to take orders for his car-starting business (which was quite brisk in the early hours of a -20F workday Minnesota morning). On busy days I'd take calls in his kitchen and batch them and relay the jobs to him, on slower days he'd just take calls in the cab. I don't remember what caused calls to go one place or the other, I don't think call forwarding was available in those days. It may have been he advertised both numbers, and just didn't answer the car phone when I was dispatching.

As soon as weather turned warmer and the car phone no longer paid for itself, he had it removed.


Reply to
Dave Garland

I was talking to a friend who I worked with before I retired from GTE, he is still there with Verizon; I was talking to him about the posts I had seen about MTS phone and I remembered that the company had activated its IMTS towers and transmitters in Hemet, Calif in the late 90's because the cell phones that we used in company vehicles had major dead spots, he told me that they just removed them last year after a bunch of micro sites had been installed in the mountains around there. He said that the 4 phones are in boxes in the CO. I asked him to see if he could get his hands on them, might be nice to have in my collection of telephone gear.

Reply to
Steven Lichter

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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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.

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 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.

Reply to
Geoffrey Welsh

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

Reply to
Ron Kritzman

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.

Reply to
Steven Lichter

An analog signal degrades gracefully. As reception becomes worse and worse, it just becomes noisier and more staticky up to the point where you can't make out what they're saying any more. There are various tricks that can be used to reduce noise. And when things are bad, words can be repeated or spelled out.

A digital signal either works, or it doesn't. So reception is good, then it craps out completely. (People with over-the-air reception of digital TV will notice this.)

Yes. And that it can easily be used for things other than voice, and can be easily encrypted to prevent eavesdropping.

That's not a digital problem, that's a design or administrative one. In fact, that situation is probably easier to deal with today than it was in the past, where the radios were crystal controlled and could only operate on one (or a very few) channels.


Reply to
Dave Garland

Dave Garland schrieb:

That is not always the case and for digital cell phone networks in most cases wrong. Even the first digital GSM networks (early 90s) used different levels of error correction for parts of each data packet, making it possible for a receiver with bad reception still to decode the most important parts of the data, resulting in lower voice quality. Even if the reception is so poor, that some data cannot be completely restored by the error correction algorithms, the receiver usually still tries to decode the erroneous data. Depending on the actual codec, this causes different problems, like e.g. blocking artifacts in the digital tv picture.

The AMR voice codec used in more recent UMTS networks, even allows the network and cell phone to dynamically switch between eight different levels of error correction during a conversation to find the optimal point on a scale between an error-prone/high effective bitrate/high voice quality signal and a robust, but low voice quality signal.

At some point, the reception is of course too poor for the receiver to do anything useful at all with the signal, but the steps leading there are far more complex than an either/or decision.


Reply to
Tor-Einar Jarnbjo

Most of these "digital" radios aren't actually digital at all. They are trunking systems, which basically operate like analogue cell phone systems.

You press the PTT button on the radio, the radio tells the repeater that it's on trunk X and it wants to talk. The repeater tells the radio that trunk X is available and go to to channel Y. You talk, the radio transmits on channel Y. The repeater sends a control message out telling everyone on trunk Z to listen on channel Z, then it repeats your signal on channel Y to channel Z.

The good news is that everybody can talk to everybody else, no matter where they are in the area, and by using multiple repeaters you can extend the system to a much larger area than with conventional simplex radios. The bad news is that it requires an extensive repeater infrastructure, and when disasters happen you can't count on that infrastructure any more.

The signalling is digital, but the actual transmission is all analogue.

Last hurricane we had, the city tower at Isle of Wight county (VA) fell down, and all the comms for everybody went out.


Reply to
Scott Dorsey

I remember RCC! In the late 1970s and early 1980s, I had a GE mobile radio in my 1971 VW van. As I recall, it was either all vacuum tube, or maybe just tube finals. I think it had a transistorized power supply to generate the high voltage. My RCC number was 248-0663. I think the 248 identified the radio common carrier, which was RCS in San Luis Obispo. It was owned by Jerry Peterson, who just died recently. I also had a tone only pager from them and used their answering service. They had a bunch of operators on cord boards. The answering service used bridge connections off the cable pair going to our shop. I don't think any sort of call forwarding was available at the time. They also operated the marine VHF mobile telephone channel. My father lived on a boat. When he came into the area and tried to call me from the boat, the operators knew exactly where I was. That impressed him! My RCC radio did not have selective calling, so I got to listen in on all the other conversations as I drove around. Jerry sold RCS as cellular telephones started to appear. He told me that he knew he could not compete with them and did not think he could get into the cellular business. The answering service is still running, but moved from the old location. All those telephone lines still show up in the old building. They put several call concentrators in there to route those lines to their new office where operators sat in front of computers (not cord boards!). I worked on that call concentrator maybe 20 years ago, so I have no idea if it's still there.

0663 Clear!
Reply to

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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I'm glad you brought that up.

I understand that until relatively recently, a walkie-talkie type radio required a crystal for each channel it could use (certain harmonic multiples could use one crystal). Unlike home broadcast radio receivers, they couldn't use that variable capacitor to select a frequency out of a band of them.

Would anyone know why commercial radios required a crystal and couldn't use that variable tuner?

Here's another question: Certain systems, such as subway dispatching and some police systems share a channel in one direction but not in the other. That is, field units could hear one side of the conversation but not the other. Could anyone explain that?

In the 1970s version of the movie "The Taking of Pehlam 1-2-3" they had a good accurate view of the Command Center which the NYC subway radio room. The big feature was radio consoles of the dispatchers so they could talk to trains. The consoles had zones, with red and green lights and [I think two] push buttons for each zone. (Don't know their meaning). I believe this center has been moved elsewhere and modernized, but the movie image was quite realistic of the real thing. (Actually, the real center was kind of dumpy compared to the movie's).

In WW II Bell Labs did extensive research into mobile radios for the military, described in the Engineering & Science book "War & Peace". IIRC, early on they chose FM over AM. Of course, other mfrs like RCA did extensive research as well. (Someone should write a non-biased technical history of the communications developments.)

***** Moderator's Note *****

The nicest part of being a moderator is that I get to see the questions first ;-).

Since I have been a ham operator since I was 13, and I used to be a Broadcast Engineer, and I hold both an Amateur Extra Class and a Commercial General Class (which used to be called "First Class") RadioTelephone license with Ship Radar Techniques Endoresement (ahem!), I think I am qualified to speak on these matters.

With Voir dire out of the way, we shall proceed to the exhibits:

Military and commercial transmitters have used crystals since the earliest days of radio: the first practical transmitters generated radio waves by use of spark gaps, which created a "damped wave" that was both very weak in amplitude and very broad in frequency. When you go under high-tension lines with your car radio set to an AM station, you're hearing "spark" transmission caused by high voltage arcing across the insulators and by corona discharge. It covers every AM station, even on the very best car radio, so you can see why it couldn't be used for long: each station pretty much took ALL the available spectrum, and everyone else had to wait their turn.

Soon after, spark was replaced with "Continuous Wave" transmitters, which could transmit much further distances because their power was concentrated on a single frequency. In short order, it was discovered that piezoelectric crystals made excellent, durable, and stable frequency-determining elements, and they are the standard for cost-effective and stable frequency-setting devices to this very day. Your computer contains one, and a computer that runs at, e.g., 1 GHz (Gigahertz) is generating that timing signal by digitally processing a crystal oscillator.

The advantage of crystal control is that it's reliable, inexpensive, and versatile: crystal-controlled transmitters will operate reliably over a much wider range of environments (temperature, voltage, age, etc.) than those controlled by Variable-Frequency Oscillators (VFO's), which use the variable capacitors you spoke of, with enough stability that in the 1970's, crystal-controlled transmitters used in "two-way" radios needed frequency checks only once per year.

Radios which are controlled by VFO's - almost all are in military or Amateur use - require constant monitoring to make sure they are transmitting on the assigned frequency or in the allowed band, and such radios often include crystal-controlled "calibrator" circuits that generate a reference signal for comparison to the VFO's setting. Of course, that won't do when the radio is being operated by a cop or a cabbie, so crystal-control is the norm.

Until the invention of integrated circuits, each channel a two-way radio could use required a crystal (in fact, usually two or more: one for transmit, one or more for receive). In other words, since each crystal generated a single frequency, each channel needed a different set of crystals.

The problem is, when you're building thousands of CB or taxicab or fire or police radios every month, the cost of the crystals starts to add up. Some manufactureres reduced crystal counts by using ingenious "crystalplexing" schemes, where something like ten crystal oscillators were combined to produced the needed output frequencies. However, this was only practical when a lot of channels were needed and crystals were expensive (as at the start of the CB craze during the early seventies), because the complicated wiring and multiple-gang switches needed to make it work also added to the cost.

Things got a lot simpler when inexpensive and easily programmed IC's made phase-locked-loop (PLL) frequency generators possible. Designers were able to eliminate all but one crystal for the entire radio, and to use a single "reference" frequency as input to the digital divider circuits which generated the "operating" frequencies. In other words, integrated circuits made it possible to leverage the stability of a single crystal oscillator so as to generate any desired output frequency with the same stability as that of the crystal source. To set the operating frequency of such a radio, a technician uses an external programming tool to "burn" the needed divisors into read-only memory inside the radio.

This is, of course, oversimplified, but it's all true. Please refer to a web page titled "History of frequency control and modern time keeping" at

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for more info.

Now, to your next question: certain systems are set up so that the radios in the vehicles can only hear the dispatcher, not other vehicles, because experienced showed that cab drivers, truck drivers, couriers, and even well-trained police officers were prone to make remarks to other mobile users which were not in the best interests of good order and discipline. The dispatcher can hear the mobile units, but they can't hear each other, because the mobile radios transmit on a different channel then the one they receive on. This gives the dispatcher control over what the mobile units hear, and also the ability to connect his receiver and transmitter in a "repeater" configuration so that everyone can hear everyone else when time is essential, as during a hot pursuit.

The rad and green lights you saw in the movie were to indicate the state of the signals which controlled access to any given section of track: as a train passes by a signal, the signal automatically goes from green to red so that any train following will be forced to wait until the first train has gone far enough ahead for safety. The dispatcher's board is a remote readout of each signal, so that he can observe the passage of trains and also see those which are not moving and may be broken down.

Last (whew!), the matter of FM vs. AM. AM (Amplitute Modulation) was discovered first and was the standard for voice (and music) transmission until Major Armstrong invented FM (Frequency Modulation). In fact, aircraft still use AM, as do CB radios, shortwave broadcasters, and (of course) AM broadcast receivers in cars and homes. FM has some advantages over AM in noise reduction, and FM transmitters are simpler than AM units, but FM receivers are more complex so it may be a wash as far as component cost.

FWIW, the L carrier used a form of AM called Single-sideband, where the various voice channels were first used to modulate a (crystal-controlled!) carrier, and the resulting AM signal was then run through a crystal (swear to Ghod) filter to eliminate one sideband, which saved 1/2 the bandwidth that would otherwise be needed. Even though it used AM, the system proved so quiet that many telephone users would hang up during pauses in the conversation, because they were so used to hearing background noise on long-distance calls that they assumed the other party had been disconnected. Bell Labs engineers had to add noise generators to L carriers, which produced the susurrus which we all associated with long-distance calls until Sprint's "Pin drop" advertising altered public perceptions.

Thanks for the trip down memory lane. They say asking an engineer a question is like taking a drink at a fire hydrant, but if you want more info feel free to contact me offline: bill at horne dot net.

Bill Horne Temporary Moderator

Please put [Telecom] at the end of your subject line, or I may never see your post! Thanks!

We have a new address for email submissions: telecomdigestmoderator atsign telecom-digest.org. This is only for those who submit posts via email: if you use a newsreader or a web interface to contribute to the digest, you don't need to change anything.

Reply to

A few years ago I was on a train with my by then old analog cell phone. Suddenly, everyone else talking on the train lost their signal (they're all going hello and staring at their phone). My phone continued to work.

Now that I'm digital I find more dead spots and cutouts than I had with analog, though very recently reliability seems to have improved.

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Too funny. I note a PowerWave repeater installed on a phone pole right down the street from me. They just put the electric meter on it so I assume it's for the MESH network the city has installed. But the more I look at it, the more it looks like it might be a trunking repeater.

I've looked for these in other parts of the city and haven't seen any yet.

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A) "the law said so." B) "precision."

next question?

Until the advent of digital frequency synthesis, crystal control was the only viable means to provide the required frequency precision and stability. If the transmitters weren't that stable, the 'adjustable' receivers would have to be more-or-less constantly re-tuned 'a little bit', to track "where the transmitter is now.".

Crystals are used in receiving gear for stability reasons -- 'precision counts' and you need to hit the 'exactly right' frequency for maximum communications range _without_ the benefit of having a continuously broadcasting signal to tweak the variable-cap to


Base stations transmit on frequency A, and receive on frequency B. mobile stations transmit on frequency B, and receive on frequency A.

"Everybody" needs to hear the dispatcher, and the dispatcher needs to be able to hear everybody. BUT the mobile units usually do _not_ need to talk to each other -- in fact, in _most_ cases, when they can, one gets significant amounts of "non-operational" chatter -- often of an informal and/or personal nature -- *with* the possibility of that 'chatter' actually blocking official traffic from the base station.

The base stations frequently operate _full_duplex_. Meaning they can receive _while_ transmitting. And, in a 'priority' situation, where one cannot wait for the base station operator to 'echo' whatever one mobile said, one can simply connect the receiver audio out, to the trans- mitter audio in. Voila! everybody _can_ hear whomever is talking 'loudest'.

With 'sharp enough' filtering, mobile stations can operate full-duplex, as well. although the -size- of the required filters tends to rule out use in standard automotive applications.

Paging (AF, RF, or IP, whatever works) the linguistics pedant! What the heck is an "Endoresement" ??

If Derwood's (sic) mother-in-law approved it, that would properly be an "Endora-sement", I believe, but this one has me perplexed.


For early PCs, that was true.

Modern units are somewhat more complicated. They generally use a VCO (voltage controlled oscillator) to running at _four_times_ the CPU clock frequency. That VCO output is divided by 2, and then inverted. _Both_ the inverted and un-inverted signals are then fed to individual divide-by-2 flip-flops, generating the 2-phase (quadrature) clock that processors need.

The VCO _also_ feeds a programmable divider chain, the output of which is fed to a phase comparator circuit, along with the output from the 'reference'

*crystal* oscillator. The error signal from the phase comparator is used to tweak the control voltage input to the VCO, making a phase-locked loop (PLL) system running at a 'many times' multiple of the crystal frequency.

Among other things, this is how one 'overclocks' the microprocessor on a on a higher-end motherboard. One simply changes the programmable divider value to a higher number. This causes the VCO to run at a higher frequency.

Aircraft communications, for one, deliberately still use AM, because some of the 'inherent' qualities of FM are a =disadvantage= for aircraft. Most notably, FM receivers 'lock on' to the strongest carrier present, to the exclusion of any weaker station on the same frequency. AM receivers, on the other hand, reproduce the audio from _all_ the transmitters within range. It is *important* to be able to hear the 'far away' aircraft calling with an emergency,"even if" a nearby plane is transmitting something 'routine'. There is the additional fact that a 'trained ear' can extract the 'meaning' from a voice communication at a far lower received signal level than the best FM discriminator can lock onto.

Note: with -very- careful adjustment, an AM receiver can pick up and render audible an FM signal. It's a bastardized use called a 'slope detector'. you position the carrier frequency in the 'skirt' of the bandpass filter, instead of the middle of it. As the carrier frequency varies, get changing signal _amplitude_ on the output side of the filter.

This is definitely in the 'waltzing bear' category -- it's not how well it works, but that it works at all.

Reply to
Robert Bonomi

snipped-for-privacy@bbs.cpcn.com schrieb:

The reason for that was probably that your cell tower was in a different location, the analogue network operated with higher transmission power or that the lower radio frequencies used by AMPS propagate more easily through buildings than the higher frequencies used by the newer digital networks. It is unlikely that the different transmission technology (analogue or digital) caused the behaviour you observed.

I suppose that this was the case with every new mobile network technology. Early AMPS users probably complained about worse coverage compared to IMTS as well. The main reason is the smaller cell size and reduced transmission power used on purpose to increase network capacity. Recently, high power digital networks, operating on lower frequencies have been installed in several countries to achieve better rural coverage, e.g. ice.net operating a CDMA based network at 450MHz in the Scandinavian countries. With relatively low network capacity, such solutions cannot however target the mainstream user.


Reply to
Tor-Einar Jarnbjo

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