Preserving a 5ESS Switch for Posterity


In June 2023, Telephone World was invited to witness the removal of an AT&T 5ESS Switch from a small rural telephone company for preservation and posterity. The following is a description of the removal and preparing for shipment to a new location.

Saving a 5ESS for Preservation

Ah, the venerable Number 5 Electronic Switching System, or the #5ESS for short. It’s been the workhorse of the Public Switched Telephone Network (PSTN) in the United States and a number of countries throughout the world. It was invented back in 1982 by the Western Electric arm of the Bell System. It was so long ago that this was developed pre-divestiture (in other words, before the breakup of the Bell System). As I’m writing this in June 2023, over 41 years after it’s introduction and 20 years after the last one came off the assembly line at the Oklahoma City works of (then) Lucent Technologies, there are still a large number of #5ESS switches in the PSTN to this day.

However, the #5ESS is sadly getting long in the tooth. Like every other telephone switch that came before it – electro-mechanical and first-generation electronic – its technologically obsolete. Not to say that it’s a bad switch. In fact, it’s still a very GOOD switch. Many telephone calls simply would not be made within the PSTN without use of the 5ESS in one way, shape or form. Over the 20 years of the #5ESS coming off the production line, there were many variations of the #5ESS. It has been used for very large central offices, very small central offices, and everywhere in between. In some cases, it’s been used as a cellular system switch. It’s also being used as a “tandem” switch that connects between large metropolitan areas. Sometimes in conjunction with a local end office switch that handles tradtional landlines, but also as a stand alone Class 4 Tandem by the AT&T long haul (originally referred to as the “Long Lines”) network. So the #5ESS is indeed the workhorse of the PSTN at least in the United States.

However, that footprint of the #5ESS is slowly dwindling. As with the advent of “packet switching” and the slow demise of landlines, the days of the #5ESS are numbered. Many telephone companies are slowly removing the #5ESS switch and replacing it with more modern technology. The 5ESS is based upon a technology known as Time-Division Multiplexing (TDM for short). TDM technology is slowly being replaced with various forms of Voice over Internet Protocol (VoIP) technology. Packet switching at the carrier-grade level is fast encroaching where TDM technologies once ruled. Like the #1AESS before it (with the last one being removed from the PSTN in 2017), the #5ESS is past its prime and is slowly becoming a line in the history books.

But before that happens, there are efforts to start preserving what’s left of the #5ESS technology for future generations to appreciate the technology behind it. The 5ESS was the Cadillac of telephone switches at the time of its introduction, and with divestiture that not only afforded the “Baby Bells” a great telephone switch, but independents who wanted (and who could afford) the best switch that money could buy. A few independent telephone companies did buy the #5ESS over cheaper and often more common models of telephone switches – notably the Northern Electric/Northern Telecom Digital Multiplex Switch (DMS) series of telephone switches, as well as the Stromberg-Carlson (later Siemens) line of Digital Central Office (or DCO) line of telephone switches.

Which leads us on this adventure I’m about to talk about. In May 2023, I was asked by Dylan Cruz (a 20 year old entrepreneur based out of Orlando, FL and founder of the NPSTN hobbyist network) to be part of a small army of volunteers to save a decommissioned 5ESS-2000 at a small independent telephone company. Sadly, I’m not at liberty to mention the name or the location of this nice little independent telco. This #5ESS had a maximum capacity of only 5,000 customers, but it’s still a #5ESS by definition. It was purchased in late 1994 and installed in early 1995. By 2020, they folded their remaining copper landline customers to a packet switch called a Metaswtich. Like a lot of small independent telcos, they are now banking on “Fiber to the Home” (FTTH) technology for being not only delivering telephone calls, but also cable TV and Internet. After roughly 25 years of service, they shut of their #5ESS. It sat vacant for three years until Dylan and his small army came along to help remove this switch, pack it into a box truck, and give it a new home down in Orlando, FL.

On June 1st, I showed up to this small telco and met Dylan, his father Marcos, and several of his friends to help dismantle the switch and prepare it to be loaded onto a truck. One of his friends, Phil McCarter, is known to telephone switch collectors. He has preserved several electro-mechanical switching systems and has made YouTube videos on his efforts. He is also a retired Telephone Central Office technician, and that’s where his expertise really helped out with the careful de-cabling and removal of the 5ESS from this small central office. We also had Joe Z, who performed a similar dismantling of a DMS-100 (the SL-100 PBX version) a couple of years previous.

These pictures tell the story better than words. We basically had to undo everything that went into making this switch work. We had to dismantle all the cabling, unhook all the cabinets, and load everything on a truck. There were three rows and 17 cabinets in all. Not only that, we also had to box up a lot of spare 5ESS parts that were no longer needed by this telco. We started on a Wednesday, and by the following Monday it was all loaded onto a truck.

The goal is to eventually hook this all back up again and bring it onto the PSTN. It’s not sure exactly where or when this will happen, but we’re looking forward to the day when this will occur. The #5ESS is worth saving, and this is one prime example of the way to do it. I’m glad that I was invited to be part of the event to document it for posterity.

Thanks (and greets) to the following:

Dylan Cruz
Marcos Cruz
Phil McCarter
Dan Lode
Austin Burk
Joe Z

Click on any picture below for a larger version


Other Telephone Historical Pages

Preserving a 5ESS Switch for Posterity
In June 2023, Telephone World was invited to witness the dismantling of a #5ESS switch for the purposes of preservation. We took plenty of pictures!

AT&T Crash of 1990
An excerpt from a magazine with details of the “crash” of the AT&T long distance network in January 1990.

Morris, IL Electronic Switch Experiment
A technical history for the first “electronic” switching system field trial experiment in Morris, IL from 1958 to 1962.

History of the (former) North Pittsburgh Telephone Company
An unofficial technological history of the former North Pittsburgh Telephone Company in Gibsonia, PA (suburban Pittsburgh) from its origins to when it ceased to exist.

Telephone Signaling System Technologies Past & Present
Details on the signaling methods used within the North American telephone network to allow central office and tandem systems to “talk” with each other.

Telephone Transmission Technologies Past & Present
Details on the physical means on how a telephone call is handled through the network between different systems.

Old Bell System Operator Routing Codes
A historical listing of old routing codes that Bell System (AT&T Long Lines) operators used to use that performed special functions within the toll network.

Old Number 4 Crossbar Toll Tandem List
An extensive historical listing of Bell System Number 4 Crossbar (#4XB) toll tandem systems from the 1940s to the 1980s.

Other Telephone History
Technological history on various telephone company systems from the webmaster’s personal perspective over the last 40 years.

Historical Videos
Various videos from YouTube that we’ve found that showcase telephone history.

Pink Floyd’s “Young List” Explained and Demystified
A very thorough explanation of the sounds that you hear during the telephone call part of Pink Floyd’s “Young Lust” from 1979.

867-5309/Jenny in All US and Canadian Area Codes
Ever wonder what happens when you dial 867-5309 in all the active Area Codes in the US and Canada?