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Northern Telecom SG1 "Pulse" PABX

Started by ....., March 27, 2016, 09:04:04 AM

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"Telephone World" has some dates for various Northern Telecom switch introductions.

SP-1 CO - 1969
SG-1 PBX - 1972
SL-1 PBX - 1975
DMS 10 CO - 1977
DMS 100 CO - 1979

I first worked in PBX installation in early 1977 and SG-1's were then being installed at a frantic pace in Vancouver.

From May 31 to June 11, 1976 a conference called "Habitat" was held in Vancouver.

BC Tel's first SL-1 was installed in the main downtown Vancouver CO for all of the Habitat traffic. After the conference was over the SL-1 was removed and reinstalled for a large bank branch in Vancouver. So this SL-1 had to be a very early unit from Northern Telecom.

By 1980 I was installing SL-1's at a hectic pace in Vancouver.



Quote from: Autonut on April 22, 2016, 05:54:49 PM
The picture of the pulse group finely arrived, I can just make out the Bell Canada logo on the front at the bottom right. Picture was taken around the late 70's give or take a few years.

Bell didn't buy these.  They were guinea pig tested in the US (on GTE) first.  The technique was a precursor to SL-1.  SG-1 was garbage, but necessary to keep the money rolling in.

It was called pulse because it took an analog wave form but it pulsed out discrete samples along the waveform, but in analog form -- short bursts.  The next step was to speed that up and then encode each pulse or burst into binary, but the way they did it was brilliant.


Quote from: Dominic_ContempraPhones on April 23, 2016, 12:29:54 PM
Bell didn't buy these.  They were guinea pig tested in the US (on GTE) first.

Maybe I should have said "I can just make out a Bell logo on the front at the bottom right."
There is some kind of Bell logo on there or am I just thinking it is?


Quote from: Autonut on April 23, 2016, 01:01:26 PM
Maybe I should have said "I can just make out if it is a Bell logo on the front at the bottom right." I shouldn't assume.
There is some kind of Bell logo on there or am I just thinking it is?

I see what looks like the outline of the old Bell logo, but SL-1 and SG-1 development were concurrent, and I remember them saying specifically that they were using GTE as a test market first.  Bell Canada probably did buy a few, but they knew about SL-1 hitting critical milestones that would quickly make these obsolete when they went on sale.  GTE wasn't privy to that information -- if they had, they probably would have held off for two more years.


The Telecom business is full of things that quickly become obsolete. If a new customer needed a PBX or an existing customer was moving, in all likelihood a new SG-1 saved the Telco money over buying or refurbishing an old electro-mechanical PBX for that customer. And the SG-1 probably kept that customer happy for quite a few years even after newer equipment such as the SL-1 was available. Buying new SG-1's in this situation is different than ramping up to replace ALL of the in place PBX's with SG-1's.

BC Tel installed dozens of new AE #1EAX CO switches in the mid 70's and a smaller number of #2EAX CO switches in the late 70's. They installed what they had to install to meet customer growth and cut over some old SxS offices where they had the room in the CO for an electronic switch at the time. In some instances if they were to add to the SxS for another couple of years to meet growth they would then be forced to add to the building to fit in a new electronic switch along side the old SxS in order to do a cut over. Installing the #1EAX freed up enough space in the building to then easily add a newer digital CO later without having to add to the building. Available space to install new switches along side the old switches played a big part in the conversion planning.

They slowed down on electronic conversions once the #2 was available because it was then known that the GTD5 Digital CO was coming next. In the case of the GTD5 it was delayed, delayed some more and then delayed yet again. In many instances we had a new GTD5 beside old SxS but couldn't cut it over due to software problems. Things were getting pretty shaky in some offices by the time they were finally able to cut over. I know of one office in a fast growing area that was cut to #1EAX, all the old SxS removed and just a few years later a GTD5 was in beside the #1EAX but it couldn't be cut into service. A trailer of SxS that had been removed from somewhere else was then put in the parking lot to meet customer growth until the GTD5 could finally be cut.



Quote from: Autonut on April 23, 2016, 01:01:26 PM
Maybe I should have said "I can just make out a Bell logo on the front at the bottom right."
There is some kind of Bell logo on there or am I just thinking it is?

The SG-1 was the result of a partnership between Bell and Northern Electric. Bell and Northern Electric combined their R&D to create Bell Northern Research, and the SG-1 was one of the first products to be produced by this partnership. I don't know the details, but me it appears that the SL-1 was a feature-creep byproduct of the SG-1. The only non-digital part of the SG-1 was the speech path, which was implemented as a 8 kHz sampled, time division multiplexed analog bus. Upgrading that to a fully digital path seems like an obvious choice. Of course, the SL-1 used a different switching architecture, but the SG-1 definitely contained the building blocks.


Good to see you back Keelan....stop in a bit more often!

If nothing else besides bringing in money for NT, I am sure that they learned a lot from the SG-1 that helped get the much more advanced SL-1 off the ground and into production.

One ironic SL-1 install that I did was in a brand new 20 storey Government of Canada building in downtown Vancouver in 1983. The GOC was on Centrex and BC Tel was just wrapping up the installation of a brand new CO DMS Centrex switch to cut over from SxS and SP1 Centrex switches as well as to provide much needed growth. There were problems and delays with the new DMS Centrex switch and with two months until the move into the new GOC building someone finally had to admit that the switch wouldn't be ready on time.

The department that I worked in was frequently called upon to help with manpower shortage problems and rush jobs from Residential installation to PBX to CO switch installation. A large SL-1 switch was grabbed from another upcoming but less pressing GOC installation and I was given 8 weeks and 20 installers to install the 1000 line SL-1, wire the entire 20 storey office building and do all the set work for the departments moving in. We got it done and 6 months later the entire building was cut onto the now completed DMS switch and the SL-1 was shipped to its original destination and installed again.

Ahh, we had lots if fun back then!