PBX

The Age of “The PBX” – 1970s-2000s

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The PBX really became something of an on site telephony product by the 1980s, even though the concepts began in the 1970s. The advent of the integrated circuit along with programs, made these ol electromechanical relics to become obsolete. And I say “become” because it would be a long time coming for that to happen. ROLM out of the left coast, had developed military spec computers and dabbled into telephony, they had gotten into the business by the early 1970s. They became successful, then came Northern Telecom (later Nortel).

 

a picture from Andy of a ROLM digital telephone from the mid to late 1980s
A standard looking ROLM telephone from the mid 1980s to even today at some sites.

The Computerized Branch Exchange or CBX was obviously a registered trademark to ROLM and brought the concept of a box making and answering calls and users would have devices that they could use to answer or place calls. Want to call out, you hit a button like 9 or 8 like you did in a Centrex setup. The system could route calls per to what a number was pressed, and block it or rout it to another set of trunks to save money on long distance.

Northern had introduced the SL1 PBX in 1975 (but not to be confused with the X11 platform since 1988 and the Avaya fusion of the 2010s). The SL stood for Stored Logic, or just code living on chips with a programed software. The SL1 was not friendly to a manager of machines, but for engineers, as well documented on this site for a number of years. This plagued into the Meridian 1 days. At this time most electronic and digital PBX systems were not as simple to choose. the SL1 PBX for an example came in about 12 varieties, between software options and hardware choices. It wasn’t like an Option 11 could cover 500 users, with 60 inbound lines today. Lot of this had to do with the computing of the 1970s.

Mitel was one of the first companies to introduce digital desk phones that allowed multiple line and feature access. Their system was called the Superswitch, and the phones were called Supersets (this is where the “Superkey” comes from even in their current VOIP carnation.) They wanted to make a PBX phone a bit more functional than a 2/500.

For some of the readers… you’re waiting on Ma Bell. Well AT&T’s Western Electric division was in no hurry to go digital, in fact some antidotes indicated that AT&T had plans to go into digital telephony by the 1990s… planned as far back as the 1960s. AT&T’s first PBX that was electronic in nature was the Dimension PBX, and Horizon PBX. For some lingering Avaya fanboys, the cabinets of these things were no modern marvel, unless you thought one cabinet holding 50 lines was a great engineering feat. A PBX scale from users/extensions to lines made sense from an economic scale for years, but when the electronics came in, boy did it take real estate. To power a 10 button Multibutton Electronic Telephone required 8 pairs of wiring. a far cry from the ol 25 pair, but certainly  for what it could do was very limited.

Turn around for technology takes several years, by 1981 the researchers at Bell Labs started to develop a fully electronic telephone network that would make the Dimension/Horizon hot mess end. ROLM’s phone systems were mostly ol 2/500s and the fancy phones were for operators. Nortel had made digital phones as far back as the creation of the SL-1, but they made their phones mimic the infamous 1A2 Key telephone system (this explains why the Nortel Meridian phones have few line buttons, and are set up for a single phone number.)

Western wanted to be unique, and this uniqueness for users stood out from the competition, they opted for use Merlin-looking telephones, but instead of having 4 line buttons directing to the outside world, use the top left row to have by default 3 instances of personal line appearances to make the phone ring, page, etc. This would be considered “call appearances” and made these phones more attractive than the MET, which sent a bit of a mixed message in the technical sense. the MET had literally Multibuttons, but not multiple lines or appearances. One call to an MET phone at a time. Want to transfer? You had to press the Recall Button, and then press a button called Transfer, then hang up.. .and it had the infamous Red and Green color indications.

The transition away from “System 75 and 85” to Definity in a 1989 TV campaign in the mainstream media

By April of 1984, AT&T introduced the System 75 PBX, with 7400 Series Digital Voice Terminals, that were a bit superior to the MET and it took several years to fix user pet peeves with the quirks of the phones, but by 1995, the 8400 Series Voice Terminals really put AT&T on the mark leading into the Avaya years, and by 2020 Avaya became an also-ran company throwing the combined history of Nortel and Lucent and AT&T into a trashcan.

For the mainframes themselves, AT&T went to extra lengths to make the system be as efficient as possible, they developed the Information Systems Architecture (a nod to what became their enterprise/carrier services) developing a company standard of circuit boards and connectors and one large cabinet could hold 900 lines. But the System 85 was basically the Dimension PBX with with System 75 hardware. There was some differences in the Dimension-specific hardware. To run the PBX’s code, required it’s own cabinet, while the System 75 could run on a single circuit board.  But to put lines and stations was equal though.

For a number of years, hospitality only used electronic PBX systems to monitor, route and direct calls per to numbers dialed, did customers get the same treatment in offices? No, they stuck to 2 wired analog phones, and the front desk typically had a digital set. Other industries may had many average users having low button phones, and more power users had the middle line, and assistants had multi buttons between 20 to 34, while the executives had the 5 to 10 button set.

The fun facts of digital PBX systems is a) the computer is technically a “phone” per to the FCC regulations on Part 68 b) and the desk phones I call just “sets” because they are regulated as Part 15 in FCC rules. c) these “phones” cannot use the regular Plain Ol Telephone provider, and are not engineered to work at home or remotely without some box. This is why I do not call these devices a “phone” but due to FCC regulation in 2018 and 2020, they see them as “phones”. The “PBX” is a computer, and it’s there where it dials out phone numbers, your “extension” is a device that tells the box what to dial using your dialpad.

Obviously by the 1990s a PBX of the 1970s that used to take an entire corner was miniaturized and could fit into a plastic “shoebox” and by taking some code and adapt it to a microcosm allowed Electronic Key Telephone Systems do function more like a PBX than an an EKTS itself. This is where the blur of what is a PBX and what should a KTS be.

By the 2000s, most VOIP vendors that had no experience in legacy voice really amped up PBX systems as opposed to Key systems. Everyone thinks a PBX, is anything that’s on site and can route a call is what everyone wants…

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Why Private Branch Exchanges was overrated (*Prior to the 1970s*)

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The Private Branch Exchange… the No Frills Approach for Saving Money on your Telephone Bills!

In the wayback of time, in the days of electromechanical switching, and you had say a 500 users… what was your options?

There was two options. Centrex and a PBX. What was the difference? One was off prem at the phone company and the other was just an identical copy of a switch, just a bit modified for an on premise environment. I should also state, that back in those days, it was not abnormal for PBX systems to be in sites less than 200 phones. The role of a PBX at the time was to have less cabling going in, allowing users to call each other by a 3 to 4 digit numbers, and be able to access to the outside world… but in those days most of the PBX was done by humans…

an image of a western electric operator station taken at the NH Telephone Museum in 2015

The operator switchboard was basically the “PBX” while in the switchrooms, was all the switching of the time whether it was crossbar or Step by Step. There was not that many features, and that didn’t come till the days of ROLM, Northern’s SL1 and AT&T’s Dimension.

There was “Cordless switchboards” that resembled the Call Directors, but it was done in a similar fashion, a call would come into a bank of lines, and the operator would buzz the extension to then patch them in via buttons. But a cordless switchboard was still a very wiring intensive devices, with many, many pairs of wires that had to be tied directly to the console.

So what about outbound calling? Before the days of electronics, a user would “dial zero” and ask to dial out, the operator would patch that caller, and either s/he would dial, or if the operator was nice, would dial the number for that caller.

The cost of a PBX, to users to lines was still cheaper, but was mostly seen in hotels, and some businesses where handling calls were important. The 1970s that brought the ability to have multiple phones and few lines coming from the telco, also brought features like station IDs (internal caller ID), Automatic Routing Selections and Automatic Alternative Routing, and anything where a computer could hear the tones and or rotary pulses where the PBX could dial for the user, rather than an operator. This moved the dialing into an electronic mainframe, but the operator still had a role to play, to answer calls, to juggle calls, and to monitor the health of the electronic PBX, sometimes outside of the States it’s called “Private Automatic Branch Exchange”.

A lot of these PBX systems were phased out with the advent of electronics by the late 1970s, but there were holdouts up to the 90s. The White House had zero electronic systems until the Clinton administration that by the mid 1990s had installed then an AT&T Definity PBX; that only had a shelf life of 3 Presidents dual terms. By 2017, the Trump Administration had prided for having a “very secure” phone system that was a Cisco, which had been a secondary system since the latter end of the Bush administration.

If you are a Gen Xer and older, you could tell a system was a PBX or Centrex by telling it’s telephone.

Standard one line phones were common in PBX setups even in the days of electronic.

If you did see Key phones, most likely it was because they were the power users, and needed direct access to lines without operators or codes. While some say the 1A2 concept was dated by the advent of electronic systems, this was critical in places where calls couldn’t get dropped because a transfer failed. In the advent of VOIP, the physics of how a call can be captured or be answered or a line can be captured… and that can be blamed to the lack of listening to customers in the world of IP… but that happened many years later.

POTD: Avaya Red 8410 DCP Telset Attitash Grand Summit Resort | Bartlett, NH

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This was taken at the front desk at the Attitash Grand Resort Conference Center in Bartlett, NH. This area in the building is where you can only spot the digital sets. The nearby bar, conference rooms and rooms use analog sets. There is no evidence of any attendant consoles ether.

I’ve frequented this facility during the spring time over the last four years for an annual conference. I no longer attend, and I like the place, so I went for the vacation this week. The people I used to see at the front desk were not working (or is no longer working there) to see if I could see the switch room.

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My Collection: Mitel 3300 and IP Phones!

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This sudden surprise came to me from Jason, the same one that gave me his old G3 PBX. This time it was a Christmas present for me. I really appreciate it. I got less than a 36 hour notice a package would come via UPS to my doorstep, to find out he had an extra Mitel system.

Without going into details, the system arrived Wednesday, the 2nd. I got a completely full fledged system capable of voice mail, auto attendant, analog trunking and what seems to be a dozen IP phones.

I decommissioned a Nortel POE switch I had for over a year to get a Cisco POE switch (since you know its best to have “Cisco all the way” – especially when I’ve made an aggressive move to use VLANs.) Simply put, to reduce manual labor of programming VLANs on Cisco Phones, it’s best to use a Catalyst Express 520 and enable CDP at the Cisco router so the PC traffic can talk to the other 12 ports and the VOIP talk to the other 12 ports. Makes life a lot easier especially when I’m introducing internet hosting to the network (next year’s project.)

 

The package came on the day that it happened to rain for the first time in years (sarcasm implied.) The UPS folks were too lazy to put the system in the proper baggy, and the package was damp, and the control unit (on the bottom) was about to break open. Factor the raw cold air, I left it downstairs for a few hours.

Using an old laptop bag for packaging material is pretty genius! (And you can’t have too many laptop bags!) On the bottom is the rack ears, which I may actually bring the Mitel over to the server barn (i.e. a small rack in the family room.)

A bunch of Mitel IP phones, I had some extra handsets, wonder if they can work on the headset jack for “training” uses, you know, hehe?

The basic Control Unit, without digital boards (in the front panel.) I’ve yet to open up the system because I believe its screwed shut, and I just found time to blog on this – as I haven’t gotten into the inside – yet.

Not sure if I have the formal OK to post this image from a private email from Jason, here is an inside of his he took for me to see.

This looked a little artsy.

I did get more handsets than telsets, and the box could’ve held about 12 Mitel IP sets. Mitels are cool in the design because the way they made it low profile. The sets are heavily curved, so a 7″ deep set of a modern Mitel equates to a 8″ of a traditional boxy telset. (These in fact remind me of the Merlin style believe it or not.) This also comes from the same vendor that made some really odd looking sets in the late 80s, ones I haven’t taken photos of. Mitel also made some really odd looking first gen screen phones. I don’t have a picture handy, and I think it’s best to try to let it rot and not put it on the Web.

Setting up the Mitel was really easy, given the dependency on an old version of Internet Explorer (the admin is about a decade old when IE 6 ruled the world – don’t blame me for vendors creating apps just for Microsoft!) and navigating through its prompts I was able to create a dial plan, figured out how to set up the phone’s line appearances, etc.

 

I got a few 5330s, their screen based sets. They are similar to Avaya’s 960x series, to not fully alienate traditional desktop users. The main information is on the top, and the lines and feature are below the solid black line. Page up through 3 pages and you can have up to 24 features and lines. (From my experiences, you can’t go beyond 4 call appearances -sometimes called “Multicall” on Mitels, but there maybe a loophole with bridged appearances.)

(You wonder how come I have “Send Calls” on the screen? Simple, you can rename feature keys or anything for that matter, which is good if you cutover from one vendor to another and try to mitigate retraining… wait, IT guys ask what is “training”?)

A caveat I learned was the blue button known as the Superkey does not work like other Mitel sets. For these 5330s, you have to program a feature button also known as a Superkey to change ringers, and other settings – for me it’s a little weird. Hardware specific on the 5330s is done on the actual blue key – which to others could be mistaken as a Superkey.

Despite other oddities, the system compensates it with very feature rich functions on the sets themselves. If you don’t get through to another user, you can activate their MWI by pressing your VM access key while ringing – which is kinda cool.

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This is an incomplete post with more pictures and video to follow.

My Collection: The Avaya 8410 Voice Terminal

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Today I’m showcasing my newest phone (prior to the last post) that is the Avaya 8410 Voice Terminal.

I’m not that creative in naming gadgets in cutesy names like dogs or cats like how people name servers, but I’m calling this one The Donald. As in Donald Trump. That guy was a long time user (to this day) a user of the 8410 terminal. What’s funny is the phone still has an AT&T label. He also uses his Spokesman speakerphone adjunct to have clear handsfree communication, even though the integrated microphone does well too.

This was courtesy from Jason, who gave me his old Definity PBX. The terms of the transfer did not include an 8410 set, which came to my surprise. He told me through email that he threw it in because there was space in the large package. More on this at a later time.

 

 

 

A closeup to that mic.

8410s were originally sold by AT&T, then sold by Lucent and then to Avaya. First generation sets were made in the States (likely at the Shrieveport Works – where most of the enterprise sets were made); when the End of Sale was issued by Avaya around 2003, the terminals were made in Mexico, despite plastic molding stating it was made here.