When I hired on to AT&T (Southwestern Bell at the time) my central office had just been converted from Xbar to 1ESS. When I retired from same central office over 36 years later it was DMS and we were testing interoffice fiber for 100 gbs circuits. I trained my entire career to keep up with technology. It was both challenging and rewarding.

Despite having thousands of parts, there’s a beautiful simplicity to the concepts and physical directness of the system. It’s fascinating to see the creativity that goes into mechanical logic systems.

Fun Fact: The first step-by-step switch and indeed the very first automatic telephone exchange was invented by Almon Strowger. Almon Strowger was an undertaker by trade. He became convinced that the manual telephone exchange operator, who was the daughter of the only other undertaker in town, was deliberately directing all calls for "the undertaker" to her father's practice instead of dividing them equally between the two as was standard practice at the time. Strowger decided that he needed to invent a way for telephone customers to dial the number themselves and used cut out pieces of paper to represent the electrical contacts so that he could work out how the equipment should work. If I remember correctly, Strowger was granted a patent for his automatic telephone exchange in 1929. Strowger's exchange required two extra wires from the exchange to each telephone to carry the dialling signals, but some clever lateral thinking allowed for using the same two wires for nearly all signalling as well as for speech.

Worked on these, as well as Planel Swt, #1 Crossbar, #5 Crossbar, ESS in my 47 year career. AT&T was a family back then, not like today.

Don't laugh, these switches were very reliable but they needed people to maintain them. I worked under the old Bell System, back in the day when employees took a lot of pride in their work. It was a very strict workplace but we were proud to say I work for "MaBell".

Man, mechanical switching....That is a trip. Just astounding the number of tiny parts involved.

"good design, a well-made product, and accurate adjustment means good service" wow who would have thought that would still be relevant today

I worked for South Central Bell in the downtown Nashville, TN central office 50+ years ago. We had four exchanges of step-by-step in that office: 242, 254, 255, and 256. 244 was a crossbar switch, and 259 was Nashville’s first ESS. I started as a frame man. Our MDF carried all six of those exchanges. Twelve feet tall and half a city block long. That means a jumper wire connecting the terminal on the horizontal or number side of the frame to the assigned terminal on the vertical or outside cable side could be over 200 feet long. There was such a jumper for each one of the 60,000 numbers in our CO. If you figure the average length as half of the max, that meant there was around 1200 miles of jumper wire on that frame, or enough to run a single two-wire jumper from Chicago to Houston.

From 1962 thru 1965 I was a dial central office repairman in the U.S. Army, both stateside and in Korea. Our telephone exchanges utilized this type of equipment and it was referred to as Stroeger stepping switches. When I got out of the Army I applied for a job with New England Telephone (their name at the time) and when I told the personnel guy what I was experienced with he chuckled and said he didn't think there was any of that equipment around any more. I declined his union job as a floor sweeper.

Today, an entire building full of those switches can fit into a small electronic box the size of a loaf of bread. Amazing progress. That said, there's definitely something to admire about the old mechanical system.

Where I live this Step exchange was fully dismanteled in the early 1990s when all of the exchanges went to digital equipment. Not only was this mechanical stuff noisy, but it housed a lot of space. Our local phone company got rid of dozens of buildings around the city as they no longer needed so much space. It is amazing how this matrix of wires, magnets, springs, and mechanics eventually connected phones together.

When I was growing up, my neighbor worked for AT&T Long Lines. He used to give me old telephone parts including switches that I wired up to make a small phone system of my own. Later as an adult engineer, I did work for SNET and New England Tel. There was a lot of SXS central offices in operation well into the early 80’s. I did a lot of work converting offices from mechanical switches to ESS. One thing we learned was that the electronic equipment needed air conditioning. Before that, telephone central office buildings were not air conditioned. This drove up power requirements and required new electrical services and larger emergency generators. Of the 200 or so Central offices in Connecticut, I probably did well over 100 of these conversions. The most common ESS was the Western Electric #5ESS They produced thousands of them in the 1980’s. At each site, a temporary building addition would be built, the new ESS installed and wired. When it was operational, the old SXS or crossbar switches removed and the new ESS was slid into the old building while in operation. The cables were then shortened, by “half-taps” (splices) and the temporary building removed. An enormous amount of work and cost.

OMG, does this video bring back memories. I was hired in '78 to install SXS in Eureka, CA. While the rest of the state was removing SXS and replacing it with quiet ESS switches. We ran lots and lots of cable, wire wrapped and soldered at the main frame and between the switches was another array of specialized wiring to connect the switches. In the 80s we were able to convert the SXS switch to dial tone by adding a small box to the rear of the switch. Those were the days, before divestiture.

I did my apprenticeship in various exchanges in the early 80's, and got to work on Strowger (what you call SxS), crossbar (which were huge lumps of metal bars with springy needles), the updated crossbar (which was huge arrays of reed switches doing exactly the same thing as crossbar), System-Y, and System-X (which was the first all solid-state equipment, and was insanely static sensitive) What's not mentioned on this video is the current consumption of those Strowger systems!! From what I remember, Leeds exchange in England drew something like 200 megawatts during busy hours, and the system had battery backups (huge lead-acid batteries) in the basement that would keep the exchange running at that current usage for up to 30mins until the diesel generators span up. Also, the heat from all those actuator coils in the electromagnets made it stifling in the summer. Those battery rooms were disgusting places too, with the stink of the acid, and as an apprentice guess who had to check the electrolyte levels regularly :) Ah, nostalgia...

When I was a telephone linesmen/cable splicer in the US Air Force from 1980 to 1994. A lot of this equipment was still in use. The first time I walked into a central office back in 1980 at Norton AFB, CA. There was a whole lot of noise in there . I asked the telephone tech about it and he replied, What Noise !. After we had a good laugh. He showed me around the CO and explain how all this switching equipment worked. I learn a lot that day.

Stumbled onto these vids and it brought back memories of my father who worked for NJ Bell in switching offices just like this one! I had parts of them as toys! The noise in those buildings was deafening, I've never heard anything like it. They broke down often as he was called in many a times in the middle of the night of course they paid well. Plus, as a kid I thought all the tools we used around the house with NJ Bell on it was normal, I think I used up my last roll of electric tape about a year ago and my Dad retired in 1985 after 40yrs. Great stuff!

You can't fully understand the impact of the computer chip without watching videos like this.

I today (February 2017) working on this kind of headquarters, you might think it's impossible, but it really is true. I live in Serbia.

I took a rotary telephone apart when I was probably 7 or 8 years old. It's amazing how many steps there were to this system. Hundreds of contacts and springs... Almost like a washing machine timer if I remember right. It's so cool to know that those contacts inside the phone, pulsed a signal in real time to these switches. Makes a lot more sense. An in old timer told me he could hear the switch box at the end of his street chattering all day long lol

Remember pay phones on the street, before that telephone booths? Remember when having to wait for a dial tone? Remember the party line shared with the neighbors across your Ally? Calling operator to connect a long distance phone call? Take a minute tonight to bring such things back to your grandchildren's memories.

You can't do this anymore, but when I was a kid I was inspired by this episode of Gilligan's Island where a phone cable got washed ashore by a storm. Their dialing mechanism didn't work correctly. So I experimented by tapping the reciever to simulate the pulsing that the dial normally makes. I called my Grandma; It WORKED! It should have worked for the Professor too.

This is absolutely astounding. As a kid, I used to like pulse dialing not with the rotary dial, but with the off hook switch. To dial a 7, I’d just press the off hook button quickly 7 times. I don’t know why I did this, it was slow and error prone. I was weird. But I remember very well using these systems. It was really crappy in terms of audio quality, but it worked when it needed to. It was not uncommon calling my friends on a line with excessive background noise I’d tell them, “this line sucks I’ll call you back on another one”. This system still amazed me. It looks like a high maintenance and troublesome system but it worked. You can even call the mainland with it (I was born and raised in Hawaii so making calls to the mainland was really neat and expensive). With the advent of Lucents amazing 5ESS digital switches and DTMF, that made pulse dialing irrelevant pretty quickly.

I worked on one of these type of telephone exchanges in the Australian Navy in the 1980's, all I can remember now is they are called 'group selectors' and line finders. Quite good to work on, mostly cleaning contacts and adjusting the mechanics.. There were exactly like this one.. I think from memory it was called a "10-100 exchange".. thanks for the vid..

I used to maintain Strowger switches for GTE in California. I don't miss maintaining Strowger switches for GTE in California.

When I was a kid, my dad was a CO manager for C&P. I would go to work with him sometimes in the summer, and often he would hand me a bottle of solvent and a pack of long, wood-handled q-tips and send me into the stacks to clean contacts on these switches. I thought it was great fun! That was a loud place to work though. Imagine an entire building with thousands of these switches all clattering all day long...

That was the time where a bug actually was a bug.

I was involved in the change out of much of this electromechanical equipment during the 80's and 90's. It was amazing to see one line of digital equipment replace an entire room full of equipment. Put a good many people out of a job in the process.

This system was in use in rural Maine through the 1970's. Very noisy, but fascinating to be in a room with dozens of these devices running simultaneously. I believe this was the first system to be put into wide use after operator-assisted calling ended.

For the time, that was some impressive technology. When I was a kid we went to the open house of UTS and toured their building. The engineer who explained these said the nickname for them was "bang and click". Fun fact: I forget the year or the Philadelphia suburb, but at this particular office these devices went silent for 15 minutes once a week, like clockwork, unplanned. It took a few weeks to realize the problem: none; people focused their attention to the "Amos and Andy" radio show, when it was over normal use returned.

After today's 6 hour outage call on our VOIP system at work were we spent about 4 hours tracing packet losses. It would be so refreshing to just go to the mechanical room to see which relay failed vs tracing some random loss 700 miles aware on a MLPS line that nobody could figure out.....

I came into the field as the last of these were going away, I dought a switch tech of today would even know what these are, let alone work on it. They were a work of art.

Some of my college friends learned how to defeat a dial lock (when the owner of the phone wanted it to be answer-only) by lifting the handset and hitting the hang-up button in the proper rhythm to simulate dial pulses.

My father spent 20 years working for Ma Bell, and part of that experience included these kind of switchers. When I was young, he described to me how they worked. But, until this video, I'd never seen them in action. Pretty nifty.

The folks that put these films on KZfaq are the luckiest folks on the planet. I absolutely love this! Wow! I'm duly and truly impressed!!

IOW, folks, the phone in your house was actually an integral part of the switching system that routed your call. Now, your phone simply says to the central switch, "I pressed the numeral nine" (if you have a land line) but back then, a rotary dial phone actually sent nine pulses to move switches in the CO nine positions. I used to own one of these Strowger switches. Note they only work in the position shown. They require gravity's assistance to work right.

When I was young, we went from the operator asking "number please?" to a dial system when we got dial phones back in 1956. This was an example of electronic (actually electro mechanical) technology being reliable from the early days on for many years without any problems. I lived in Huntington, NY at the time.

I remember doing banks and wipers on Se50 and type 2000 switches back in the early 70s in Telecom Australia. You had a tool that was shipped in a curve to wipe and clean the switches. This brought back many memories.

Even today with our "digital miracles" This and the original automatic transmissions still freaking amaze me!

I absolutely love all of the sensations of rotary phones- the look, feel, including the timing and waiting between numbers and sounds are very satisfying for me and I miss my rotary yellow doughnut shaped phone a lot!

Tapping out a number was a useful skill when a phone had a dial lock. You had to get it just right or you’d get a wrong number. The lazy way was to only learn to dial zero (10 taps) and ask the operator to connect you because “something is wrong” with your dial.

This certainly brings back memories. I worked for about 2 years doing routines on these. They had to be lubricated and timing adjusted and checked. I wish I had taken a couple of these when we changed to crossbar and then 4e. I helped cut the Dayton Ohio office to 4E.

I worked for the phone company in 1970 when this was still in use. The #5 cross-bar (touchtone) was just being tested and put into service, in Los Angeles. and the switchroom was very noisy, with about 20-30 'walls' of these switchers, the film here just shows part of one wall, or rack as they were called. New guys in the switchroom got a year or two of cleaning and adjusting these things.

Funny thing is, even to this day electronic phone switches for analog landlines have to be backward compatible to dial pulses in case someone is still using a rotary phone somewhere.

My first job, at GTE. Working in a step by step central office from 1968 to '68. This was a real trip down memory lane. Knew those switches well, and all the parts and maintenance routines.

Wow, I never realized there was so much MECHANICAL engineering involved with the early phone system. That's some fine engineering there! I'm an electronics guy myself, but I have much respect for the Mechanical people.

I worked for Telecom Australia as a communications technician when the exchanges had step-by-step equipment, like the others who posted here we had pride in our skills and workmanship. Eventually step-by-step was replaced by the Ericsson "crossbar" system which had central control units albeit comprised of electro-mechanical relays - a foretaste of the future's all-electronic systems. We used to joke about the "telephone exchanges of the future" which would have a staff of 2 manning them - a man and a dog (the dog to guard the building and the man to feed the dog). I used to think "Naaah it'll never happen". I left Telecom ages ago but I notice the modern exchange buildings in my area seem to be unmanned and visited by maintenance crews.

I'd often wondered how the older rotary system worked. That's quite fascinating! (Even for someone born in 1990. 😉)

This equipment WAS reliable. Far more important reasons for replacing it to reduce the number of employees included far lower power requirements, faster processing of calls, and making available features such as caller ID, call forwarding, all waiting, number portability, and many, many other features that we take for granted today. Yes, I also worked in Central offices or many years, on these switches, and also through most all of the later ESS switches, both analog and digital.

After watching the 1938 and 1969 operator instructional videos it's interesting to see this but what I really want to see is the motions an operator made to change circuits and how easy it might be to mix up with another circuit and how quickly they were expected to find the right circuit.. and how that system works as you're showing here with phone dialing. I remember rotary phones. I was born in 1975. I actually used a rotary phone up until 1993 I believe. From there we quickly got better technology and now alot of homes don't even use phones. The cell phone was slow to start but it's made a huge change to your business I'm sure. At least you guys have a cell service too.. at least last time I checked.

We called them Strowger two-motion selectors when I joined Post Office Telephones (later British Telecom and then BT), in the UK in 1973. Some of the large exchanges had selectors that looked identical to these, but most had a more modern version, with a squared off front and was not as tall, which I believe were referred to as '2000-type'. In UK exchanges, the hunt for the initiating subscriber was done by a rotary uniselector, but otherwise the process was pretty much identical to that in the film. They were indeed subject to intensive maintenance, and every selector in the exchange was routinely 'busied out', removed and tested, with adjustment and/or replacement of components done as necessary. I only stayed for about 4 years, and crossbar was making its way into the network at a rapid pace. I can remember how much cleaner, brighter and quieter the x-bar exchanges were than the old strowger ones.

Most of the old timers I worked with in the COs were profoundly deaf, and here is the explanation why. I started in the CO, both 5E and DMS and retired from cable repair. The era of fiber switching will be just as revolutionary.

As an IP networking professional, all these switches and discreet circuits blow me away

Older stuff like this is actually easier to understand and greatly fascinates me

Right now I'm literally sitting in the same room that these or a variant would have been in many years ago. They updated to DMS100 in the 70's ish which is in another room in this building, and it's been running since with zero downtime. It's neat to see this old tech, and how things changed. POTS (and rest of telecommunications really) and everything that goes into making it work is something often taken for granted.

The engineering skills needed to make this type of equipment were not much different that today. Instead of mechanical design we use digital switches guided by "code" written by equally skilled individuals.

I love the smell of trichlor in the morning!!

Absolutely awesome to see and learn the mechanics behind these old switch banks.

I actually have this unit in my workshop at home, Cool Stuff indeed, makes you appreciate the evolution and engineering of the PSTN, i feel honoured to have been given this piece of hardware as a gift from Telstra Staff, due to the mere fact that i showed high interest when attending the telecommunications museum in melbourne. i still can't believe i own this hardware....... unbeleivable but cool

I love old technologies. Magnificent. Great video.

My dad's first job with AT&T in 1947 was as a CO repairman working on these.

03-26-2020 watching while covid19 stay@home. Home to see you in 20 yrs.

I remember a school field trip to a central office in the 50's The clicking noise from all the mechanical switches was deafening..

The Franklin Institute, a science museum in Philadelphia, used to have an exhibit in the 1950s that demonstrated stepper switches, similar to the device shown here. It also had a Univac II computer on display, examples of dozens of clock escapements, a magnetic brake, and lots of other interesting basic technology, in the days when visitors took the time to learn about the exhibits. It had a re-creation of a realistic Nickleodeon, a theatre that showed silent films with a live organ accompaniment, including a roll-down advertising curtain in front of its stage. This theater is long gone. Today, like other science museums, so it can survive, it caters to the current public taste, such as its Space Command exhibit about outer space, and by offering light shows in its Fels Planetarium. Fortunately, it still features a moving 350-ton full-scale steam locomotive indoors.

I love old telephone technology. Heck, I love ALL telephone technology. I worked for Bell Labs for about seven years back in the 1980s and got to play with 5 ESS switches, the 3B20D computers that ran them, and learned all about this little thing called Unix. :-) My last two years there I worked on the Autoplex 1000 cellular switch. I was in the lab the day we switched our first call. I'll never forget it. Man, I loved that job. It just wasn't the same after Divestiture. (Boo, Judge Green, boo!!)

Digital switching also used this logic. I saw a similar thing at a museum in Georgia. It was comprised tall, cylindrical switches. I was training in the US Army's Signal Corps.

When I was young I used to practice using the cradle buttons to send the pulses to the system instead of the dial. the buttons had to be clicked down at a steady rate in order to complete the call.

I love seeing your old archive footage the work that was done was incredible.

Here is something I tried as a kid and it worked, instead of dialing the number, click the hangup button quickly, like 5 times in a row for a 5, do this for all the numbers with a pause between them and it connects to who your calling normally.

Ahh ! The sweet sound of a line finder, selector and connected !

Nice to watch these old documantaries. Thanks for uploading.

This is really cool to see. I have listened to pretty much all of *Evan Doorbell* audio files he hosts on his website but had no clue what the actual vintage SxS equipment looked like.

Dr. Stroeger, a dentist was the inventor of the step by step switch. The patents for it were actually held by AUTOMATIC ELECTRIC, the development and manufacturing arm of General Telephone (GTE).. while BELL LABS and Western Electric with the development and manufacturing arms of the Bell Telephone system. The work at BELL LABS is directly responsible for the digital world we now live in.

Amazing how far we have come.

Early in my career i used to work on this equipment. Miss those days

A fun step back in my life. When I was getting out of the Army from my first enlistment, I signed up for a course called Project Transition, to prepare me for a job in the real world. Well I always had a deep interest in radios and telephone so I took a course in telephone central office repair. What it amounted to was to intern with the engineer who operated the switching central for William Beaumont Army Hospital, a brand new building (in 1972) with a brand new switching central that looked exactly like the one in this film, and operated the same as well. I learned a lot from that course, and I was all ready to go to work in a central office, when my wife found an add for police officer in my home town. The add said "MUST BE A VIETNAM VETERAN!" well I qualified for that requirement, so I sent in an application. I never heard back from the City, so I figured I was not chosen, the only reason I even thought about it was that my brother-in-law was a cop and I really respected him for his dedication. So I get home from the Army, having driven from Fort Bliss Texas to South Dakota, and I am home for exactly 6 hours when the phone rings, it is the town mayor, who asks me where the hell I have been, well I told him on the road, seems they had been trying to call me, I was the only Vietnam vet who applied, and they had this grant that would pay my wages for six months so long as they hired me for a guaranteed 1 year, but I needed to be sworn in on that very day. So it was I began my career as a police officer riding along with an officer who would turn out to be the Chief about three years down the pike in blue jeans and a police jacket, with a pistol on a holster hooked to my old cowboy belt.

So much work went into these systems. Amazing that they got reliability.

Beautiful, I really enjoyed this video, thanks for posting it. Another example of a great accomplishment which happened mostly behind the scenes and which most people never gave a thought to.

I worked on this starting in 79, also Strowger rotary exchanges from the 30s. In early 80s we switched to NC400 crossbar but nobody understood them so they were quickly changed to solid state. I still have fond memories of maintaining step by step and even oiling the tone generator.

So much time must have gone into the machining of all that equipment.

Beautiful devices, fascinating to watch them in action. The technicians must have been highly skilled to maintain them in perfect working order.

Seeing slo-mo done in the fifties really has its own vibe. Love it

I remember when you could dial your own number, get a busy signal, and talk to other people through the busy signal!

Absolutely amazing. I wasn't expecting this kind of electromechanical complexity. I thought I'd see a bunch of valves (emulating transistors) or something like that.

I worked with this type of office. “ Bank n wipers” we use to say cus you would spend most of your time on maintenance of these switch selectors.

T mobile still uses these to this day.

Good old stuff,it was great making these things in my youth,the factory was nearly 3000 girls strong, us apprentices were kept busy!!!

I worked for GTE for 3+ years and, amazingly, it's the GTE switch GTD-5 that became the standard for ISDN - Integrated Services Digital Network - the "internet". It's engineering arm, "Automatic Electric" was as innovative as AT&T's "Western Electric". The companies together built the industry and what an industry it is. Imagine, ... making money from people talking.

this brings back memories, I use to work o these types of switches back in the seventies when it was being replaced by digital systems.

I freaking love this! Love love love electromechanical switching. I have old traffic light control boxes made by Crouse-Hinds That advance the traffic signals in virtually the same way.

Nostalgia. I started working in the telephone industry when many SxS switches were still in service. I went to work for Northern Telecom (Nortel) in the '80's selling DMS-10's & DMS-100's to independent telcos. Made a damn good living replacing these switches with DMS digital switches, which of course are now obsolete in their own right with many of them being replaced by IP based softswitches.

Good service is something companies have now clue about no days. Good in general is something most people don't know much about now that I mention it.

I work in VoIP, practically doing all these same things via servers. The transformation from networks and switches like these to the internet tech we have now is hard to imagine.

Don't just write this kind of thing off as "old". You really have to respect the precision work of engineers that made it possible given the state of technology in their day. The principles that it runs on are just as valid today. Technology doesn't become obsolete, it's rather the *products* of technology that supersede each other. Technology isn't a physical thing. It's the study of techniques as they relate to fabrication.

Bell Labs invented the transistor to speed up the telephone system. It took a while to get solid state switches going.

Great video, yes this equipment was. Very reliable, I remember endless rows of these switches. Incidentally I thought they were called STROWGER SWITCHES.

What was cool was hearing them work.

I worked as maintenance employee for a Dutch telecom operator Al this electro mechanic exchanges work at the same way Like Philips UR Maintaining this kin of electro mechanical exchanges is very expensive Thank you for the upload

I remember watching a Step Switch in the early 80s at a Military Base. they did had the SL and SP Switches too, but part was still Step, a few years later it was mostly DMS

Why are these old educational films comforting?

It only shows you the operation side of the equipment, when it comes to manufacturing of those equipments... Unimaginable.