This video identifies and explains the components of the 551A PBX cord switchboard and demonstrates how intra-PBX, outgoing and incoming calls are processed.
This is the only video I could find where it explains how and why and with what logic and reason the operators were plugging those jacks. And I've looked for hours and hours. Thanks.
@@michaeljones5681 Well this 551A PBX is the most basic of switchboards. The telephone company toll switchboards were much more complex and interesting. If you're curious to see how operators processed long distance calls to and from payphones, look for my video "The 3-Slot Payphone Part 1". Just search my channel name, Hicken65, on You Tube. Thanks for watching.
In the 1960, as young boy, I operated this exact system in a hotel in North Dakota. Your video brought back such wonderful memories for me operating this system. I knew exactly every move you shared on this video as a young boy. Thank you ever so much. 😀
I enjoyed the video. As a retired NW Bell telephone employee I worked on the 551PBX several years. I had the pleasure of upgrading the customers service by removing the 551BPX and installing the new (at that time) WECO Dimension 400PBX out with the old and in with the new☎. It was an eye opener for the customer to see their old service disappear and the newest processor controlled programmable PBX switch take it's place. It was an amazing change for the company operator back then. I was able to obtain the 551PBX from WECO after it was removed from service back in the mid-70s, and I still have it today, although it's not connected and remains in mothballs at the house.
I can’t tell you how long I’ve been looking for a video like this! Wonderful job explaining things. I’ve yet to find a more informative video on this subject.
As someone who was an early adopter (ver 0.6, 2003) of Asterisk IP PBX, I’m amazed by the simplicity of this system. Also, many of the same terms were still in use at the time, all those years later.
Thank you kind sir for showing that demonstration. I have always had a fascination with switchboards and this was a wonderfully explained and demonstrated example of how it works. I thoroughly enjoyed it
That was a very clinical and informative presentation. Fascinating! I always wondered how that worked. We had a hotel here in town that still used a switchboard until the 90's. They didn't want to give it up because they charged for all calls made.
This video was fantastic! Lately I've been obsessed with how old telephones and systems worked- especially the switchboard. This explanation of the simpler business switchboard was perfect! It was just what I was looking for. When I worked in an office in NYC starting in the late '70's, there was an old switchboard in the reception area, with a woman operating it, plugs and all! Thank you for making this well organized video, and your other ones as well!
I had the opportunity in the late 70's to work for a Wall St. company that had a 5 position manual switchboard. I think it was a 701 board with 555 equipment. The method to answer the trunk calls was the same, and there was no automated ring, you had to pull the key to ring. Callers would sometimes think they'd been disconnected because they couldn't hear any ring tone. I made friends with the chief operator and she let me run the board from 8:30 am until 9:00, when I had to be at my desk. I loved working that board and regret that when they upgraded to Centrex and dismantled the board that I didn't buy one of the positions.
I was a switchboard operator for the Air force, and used a three position switchboard just like the one in this video. Good job explaining its operation.
My wife and I were in Tellico Plains in eastern Tenn. and visited the switchboard museum. We spent several hours investigating all the different switchboards :-) Enjoyed the video, thank you sir :-)
I was an operator many moons ago---- would STILL LOVE to have a switchboard station position here... this brings back some very pleasant memories, and a few bad ones.... thank you so much for sharing!
Thank you for uploading this very comprehensive tour of this switchboard. It reminds me of a story told by a friend of mine who was a telephonist in a large manual exchange here in the UK. It was Christmas Eve, and surprisingly there was not much traffic, so she truned around from her position to talk to the Officer in Charge.She responded by asking "Are you attending your position Mrs H.?" To whit Mrs. H. responded "Well, there's nobody calling!"The O.I.C. retorted "Well there might be!" - But such was the camararderie amongst colleagues that they took it good spirit, and carried on. During recovery from an illness, I built my own magneto switchboard 1 + 9 ,from basic parts. Even took an international call from Los Ángeles and forwarded it to Ext 1, my daughter's room."Have you finished?" I'll hang up and ring off now!
I was so confused on how these work when watching the Crown on netflix. Looks for ages to find a video and this was the best one. Thank you for answering so many question I had 😁
Well, as you saw on the Crown, placing a call to the Queen was much more complicated than merely patching through a PBX switchboard. But I'm glad my video was helpful to you. Thanks for watching.
Most excellent video. I especially appreciate your patient explanation of each detail of the switchboard. I collect and occasionally restore antique devices (radios, telephones, the occasional clock), so this video was fascinating to me. I found myself here because of an old episode of The Waltons. On the show, Miss Tatum was training Erin on a similar switchboard. And I became curious about the actual operating procedure. Thank you so much!
The voice of the man explaining everything sounds just like the voice of the narrator who speaks on celebrity biography, videos...very slow,concise, and clear.
Wow that was a fantastic demo. It's an old piece of equipment where every connection was quite manual and physical contact with the wiring was needed via the plugs. It's interesting to note even the ringing was manual and the 2 seconds of ringing followed by 4 seconds of silence had to be done manually. We've come a long way since then. It's cool to see this old stuff. Thank you sir.
This was an EXCELLENT tutorial on how to operate an old-time PBX switchboard! It's also interesting to note that these switchboards were manufactured by Western Electric, and this particular switchboard was in use at a hotel in Michigan City, IN. Thank so much for sharing! I'll be liking and subscribing for sure!!!
@@Hicken65, my mother was an operator all her life and I relived all those experiences as a child when I visit her at work and now, thanks to you I know how the switchboard operates. Thank you once again for bringing back all those memories!
Thank you for the video, I retired from Verizon after 38 years. I was a central office technician and worked on 1E, 1A & 5Ess central offices. I've seen many switchboards but did not know how to operate one. Your video is exceptional.
Well, thank you very much and thanks for watching. If you are interested, you may want to check out my other telephony videos. Just search my channel name, Hicken65, on You tube.
Enjoyed the video, as well as your videos on the stepping switches. One of my hobbies is restoring vintage jukeboxes; their remote "wallboxes" used a similar, albeit simpler, electro-mechanical stepper circuit. It is truly awesome that these systems worked so well. And still do!
I used to work for southwestern bell as a SxS switching tech in the 70's but always wondered how the manual switchboards worked. Thank you so much, this has been very interesting after all these years.
I'm trying to knock together a video game prototype in which the player has to operate a 1920s switchboard and I feel so lucky to have found this video. Thank you so much for making it and going in such detail especially regarding all the different scenarios! I was trying to find a user manual online but this is so much better.
Thank you, good sir. Just bought a similar switchboard and it's encouraging to see one in working order. "Mine" appears to have been home to some rodents for the last 40 years or so and is not currently operable.
Just cleaning up its appearance makes it a classy looking antique. If it's a hobby you enjoy, a full restoration to working order takes a lot of time and effort, but the results are quite rewarding. Thanks for watching.
Absolutely excellent video. I was looking for a video that would clearly explain how these phone stations work. Thank you for sharing your knowledge in a easy to understand tutorial.
Thanks for sharing a very thorough and informative explanation of this wonderful piece of Bell System hardware. I never knew where the term "hoook flash" came from until now!
Thank you for this great video. For the last six decades I have been curious about how a PBX operator board works, having watched hotel telephone operators use them in the 1950's. I always knew the cords connected to outside trunk lines and phones in the hotel, but I never understood how the switches and keys worked. Now I know, and so I am ready to become a PBX operator at any hotel who will hire me !!
Well I'm glad I was able to satisfy your thirst for knowledge. You might also like my videos on rotary dial switching equipment. Some are very long and detailed and some are reasonably short. Just search my channel name "Hicken65" on You Tube. Thanks for watching.
I was about 6 or8 years old when one night my cousin Cathy took me to the NYC Columbia University switchboard and showed me much of the operational info found in this video. I immediately completed a few calls on my own.
That's the beauty if this switchboard . For any business, any employee could be trained to use it in just a few minutes. In addition, the operating instruction are posted on the board.
Finally, no more mystery about how that dang thing works. AMAZING how far we have come with phones. I remember ditto machines from when I was in grade school, Xerox hit the mass market when I was in high school. Did you ever build something with Heathkit. My dad build a color TV, ha ha. BTW, TVs, remember having to turn the dial to change the channel? No videos, 4 channels plus the educational. Old B&W movie or TV show reruns were the choice when fresh local or network TV programs were not being broadcast. Thanks for the post, much appreciated!
I also remember that the TV used to go off the air overnight. When it came on in the morning , it displayed a patterned test card that allowed you to adjust the vertical and horizontal alignment of your picture (after your tubes had fully warmed up, of course). I'm glad you enjoyed the video. Thanks for watching.
Many decades ago, I was working of converting a PBX board, like the one in the video, for use with magneto phones in a summer camp. The circuits from the phones to the switchboard were modified by adding a latching relay. The current generated by the phone's magneto would close the relay keeping it locked, lighting the jack lamp. When the cord was taken down, the locked relay was released.
Thank you so very much. Ive had limited exposure to a plugin board years ago. Then the world changed to electronic and digital... Wish I was born in the era when these exchanges was the norm.
I started working for a telephone company when I was a teenager and it was the era of cord switchboards and electromechanical automatic switching systems. I worked in a central office troubleshooting and maintaining all this equipment. I have nothing but fond memories of those days. Thanks for watching.
I bought one of these PBXs at the Rose Bowl swap meet in the early 1970s Set it up in my Callabasis home with 1/2 dozen vintage phones including two Ericsson Eiffel Tower commemorative phones for the Paris Worlds Fair a desk set and the wall model which I found out much later was quite rare.
In working condition, these boards are a joy to demonstrate, especially if it's a hands-on demo for kids. Your setup would have been an impressive sight with those phones. Thanks for watching.
I really enjoyed your video, but I have a minor nit to pick: In all of their training material, WECO referred to the person handling the switchboard as the "Attendant", not the "Operator" - Only Bell hired operators. GM had attendants :D Thanks for the exhaustive demo!
Glad you enjoyed the video. You're absolutely right, of course, about the word "attendant". I just felt the word "operator" was more in tune with what people would recognize as the name for the job, regardless of whether the switchboard was located in a PBX or in a Telco central office.
I have always wanted to know how these boards worked. Thank you! I was a telephone operator for Sprint LD from 1992 to 1996 although our job title was Customer Agent. Everything was done on a computer so we really had very little control over the calls. Loved international calls the most.
I think you would really have enjoyed working on the old long distance cord switchboards, in particular the type 3CL. They were much more complex than the 551A PBX, but lots of interesting different tasks to perform.
Simulated Operation 25:14 -- call between extensions or stations in-house 34:23 -- call outside line 38:00 -- receiving call from outside line 44:12 -- use of buzzer 45:00 -- call outside line without operator assist (night-thru operation) 46:36 -- use of hand-crank
Fantastic job explaining fantastic designs by gifted people that said this isn't going to get done by itself. I'm just going to say, used to be lots of related surplus available and was Absolute Quality and almost always from heaven for busy people teachg people how to be busy for NS( I have to say this ) hundred's of approches in basic area's of elect.that started in Pittsburgh🇺🇲 just walken the dog & some know exactly what they're saying for one transistorized reason.
Hicken65, I used to work for AT&T as a telephone operator 20+ years ago. The cord switch board had already been phased out and we were using computer terminals to help customers complete their calls. I wish I had worked using a cord switch board like this one. I've always been fascinated by them. Thanks for the video and for your reply.
Thanks You for Your video. There is a some of documents about old PBX but Your video gave me answers to lot of a questions. I saw in another document that the operator tested something by touching the plug on the ring of the jack. Maybe he finding free or funkcional lines and he listened if it clicks in his headphones? Several years ago I created my small PBX from FreePBX and one analogue card connected to the public telephone network. I had to learn a lot about the analog phone line. How hangout detection works, etc. I was happy as a little boy when I made my first phone call through it. I really like old analog phone lines because if was a problem, blackout or something like that, analog phone lines was work still thanks of their large central batteries and minimal power consumption while VoIP phones was silent after a few minutes as soon as the first UPS on the way of network was discharge. Thank again and sorry for my english...
In a single position PBX switchboard setup, when an operator is attempting to complete a call to a PBX station, she/he can tell if the called line is busy by looking at its jack. If the jack has a plug in it , it is in use. If it doesn't have a plug in it, it is idle. In a multiple position PBX switchboard set up, the PBX line jacks are multipled to each position. An operator can't tell if a line is in use just by looking at its jack, since the line may have a plug in its jack at any other position in the multiple lineup. If the line is in use, tapping the sleeve of the line jack with the tip of a cord plug with its associated talk key operated will cause clicks to be heard in the operator's headset.
Thank you so much. I've always been fascinated by vintage phone equipment. The Strowger switch is one the most amazing invention. I would love to see behind the old ceiling to floor switchboards. Early on, they would only hire male operators, the job was considered to strenuous for women.
I worked on one with 50 jacks and when covering night shift five of these equaling 250 jacks but of course not all that busy overnight. During the day we had five operators.
As you might imagine, back in the day, large businesses with thousands of telephones would have very extensive switchboard lineups. Thanks for watching.
I worked a plug & pulley system in a UK hospital. The plugs came from above and also infront You could hear the weights and pulleys moving behind the unit as you pulled the cords. Outside line requests had to be patched over to another board in our line. I remember patching a call to hospital block 3 and then having to use the dial to call a particular ward or nurse station. It was always very busy.
Thanks a lot man for making this in depth video of how to use it! I applied to be a phone operator for this summer at an old resort in northeastern Wisconsin. They showed me the equipment which I'll be working on and I was really shocked they were using something like that. Im pretty sure this is the exact same board they're using in the resort. But anyways, thanks to your video, I now have a basic understanding of what to do! Now I'll look like a pro on my first day of work!
Very nice presentation! You've covered everything I wanted to know. I'm curious, how did you go about wiring lines and trunks to the unit? I've wanted to get one of these for the house for the last few years. Someday.
While watching this video intently I felt I was back in the 30s and therefore I had to laugh when I saw that futuristic Jetsons device sitting on the right lower corner of the switchboard desk. And it was wierd when a call was placed through the board to that "miniature telephone of the future."
Important information to add about busy lines: If this were a multi station board, the operator would not know if the called party was busy. So they would need to touch the tip of the front cord to the sleeve of the called line and if a click were heard, it was busy. Not needed on a single station board but needs to be mentioned.
Great video. I grew up in a small Indiana town where local service (not to mention long distance) was handled manually by cord boards, and naturally all PBX service was on cord boards as well. I found a 552 on Ebay years ago and wanted to restore as you did with yours, but didn't know that the circuit gate was often removed when these boards were removed from service. Obviously, there's nothing to be done with my 552 without its circuits. Any idea if boards are ever available complete with their circuit gates? Thanks!
Crobertg10, You don't have to go all the way to the 30's, just back it up to 1980 I was working back then on " cordboards " until 1992 we got the last cordboard removed and went on to D.I.D. phone service. I must tell you that I miss the cordboard, imagine having them since 1952 until 1992 that was the longest relationship my boss ever had. Good memories !
This is an awesome video!! Loved every second of it. Best explanation of how these things worked. I do wonder though, what about areas where there are hundreds if not thousands of local subscribers. Do they have substations within a "pbx call center" and transfer them within that area? In other words, trunk lines are for long distance but would they have "local trunk" lines that would go from station to station? Seems like that could be quite chaotic. Again, loved this video!!!
I'm not sure I understand what you're asking, but I'll give it my best shot. PBX's , or Private Branch Exchanges, are telephone switching systems for businesses.They can be very small, like the one in this video, or be very large, large enough to handle several thousand employees in a business. If a business has more than one location, it can have a PBX at each site. These PBX's can be joined together by tie trunks, which handle the calls between the PBX's. The telephone network that the general public uses is called the Public Switched Telephone Network (PSTN).The switching equipment units for the PSTN are located in telephone company buildings called central offices. Small to medium sized towns would have only one central office. Larger towns would have two or three and cities would have several to dozens. Generally, all the CO's in a town or small city would be linked together with direct point to point local trunks. Larger cities would require one or more tandem switching central offices. With the tandem arrangement, the local trunks from the CO's would be wired to the tandem CO.The tandem CO would simply switch incoming trunk calls to outgoing trunks. I hope that answers you're questions. Thanks for watching.You may be interested in my other telephony videos. Just search my channel name, Hicken65, on You Tube.
A PBX would only be used in a private business with many phone stations, like an office or a hotel where each room or desk has its own phone. That's why its called a Private Branch Exchange. The trunks are outgoing lines. The 15 holes in this case (maximum of 40) are the internal phones. The operator can connect any of the 15 phones to each other if one desk wanted to talk to another desk or the operator could connect up to 6 of the 15 to an outside line by connecting them to one of the trunk lines.
Thank you for making this explanation with such depth and for showing examples of each possible scenario. Now the whole process seems a lot less random to me when I watch other videos of boards in operation. I would assume that the "night-thru" operation would only be workable if the phones connected to the PBX all had dials of their own? Or could someone key the receiver repeatedly on a phone at the dial tone and talk to a remote operator?
Well, it certainly was in its day. Common battery cord switchboards to process subscriber calls were the staple of the Bell System for 20 years (1900-1920) before they began to venture into dial systems. Thanks for watching.
Great explanatory video! What's not clear, but I assume is the case, is that when in the "barge in" key-forward mode on either row of keys, both parties can hear the operator -- the operator can't speak to only one party. What's interesting is that the front keys are used instead of the rear keys when the initial station connection is made instead of the rear row. What would happen if you used the rear talk key instead?
Great video showing each an everything in a glimpse. Thanks for the publication. Really needed to find something like this. By the way, do you have anything on the next evolutions as the Strowger switch etc?
Thank you for the explanation of the operator board! So, this switch board would be a block of home or business in this section / block? So, question if you are calling outside your block area you would have be connected to a different station?
This switchboard was not a telephone company switchboard that served residences and businesses directly as part of the Public Switched Telephone Network (PSTN). Instead, it was designed to work as a Private Branch Exchange (PBX) to serve small businesses that required 40 or less telephone sets to run their businesses. For example, a business with up to 40 employee work stations in an office building, or a motel with up to 40 guest rooms. Incoming calls from the PSTN or outgoing calls to the PSTN were handled by two way trunks that connected the switchboard to the PSTN. These trunks were located on the bottom row of jacks on the switchboard and are shown in the video. I hope this answers your query. Thanks for watching.
25:14 Thank you! Because of a video comparing technologies, we had a discussion how making a call worked before automatic dialing was a thing. And, at least from my search results, it's hard to find footage explaining how it worked in detail! I knew they used plugs and jacks, but I didn't know why. So one question. Did I understand it right, that a PBX station could only work with a fixed number of phone numbers? And as soon as you request to talk to a number outside that station, I assume, they send you to an in-between station that routes you to the other PBX station that has that number on their board, right?
Every PBX cord switchboard had a design capacity that defined the maximum number of telephone jacks it could terminate. On my 551A switchboard, that number was 40 jacks, but PBX switchboard designs ran all the way up to several thousand jacks to satisfy the requirements of large businesses. When several hundred or more jacks were required, one operator would not be able to handle the traffic without severe delays, so the jacks were multipled to as many switchboards needed to handle the load. So, for example, a business with 3000 telephone extensions may have had 10 switchboards, each with 3000 jacks wired in parallel across the 10 boards, serving the same 3000 telephones, but with 10 operators handling the load. Some businesses had more than one geographical site in a city, and each site would have its own switchboard(s) and telephones. There would be trunks between the switchboards at each site to establish connections between the telephones at any of the sites. Sometimes, a business with only one switchboard would outgrow its capacity and add a second one to handle the growth. In such cases, there would be trunks between the two switchboards to handle the calls from telephones on one switchboard to telephones on the other switchboard.
first of all thank you for making such a great video and explaining all these functions i hope you or anyone else is still answering questions: 1. what happens if the operator accidentally rings on a established connection? 2. if the operator would switch multiple switches to the back position would that be some kind of conference (would all stations be able to here each other through the connection made through the operater's jack)?
Question #1 If the rear key is operated to the ringing position, the station connected to the rear cord will hear audible ringing tone through their receiver, but it is somewhat louder than audible ringing heard on a normal telephone call. The station connected to the front cord will just hear a click when the rear key is first operated to the ringing position. This situation is, of course, reversed when the front key is operated to the ringing position. Question #2 If the the front keys of more than one cord position are in the operator's TALK position (back), then all stations connected to these cord positions can communicate with each other. Thanks for watching.
Would it be possible to get a high resolution photo of the schematic on the rear side of the board that protects the relays and such? The link provided below has a PDF version that was converted to true black or white (like a FAX). You have an awesome resource and I would hope it could be preserved as a high quality digital image. Thank you for the video!
Next time I need to do some maintenance in the back of the board I'll take a picture, but i don't think my existing camera would produce a high enough resolution for what you're looking for.
Very nice detailed explanation. I just got a board like this (from your description mine might be a 551B) so now I'll have to carefully separate the multi-pair cables and try to trace them out. I do not look forward to reading color codes on 70+ year old cloth insulated wires. And then I have to figure out which pair gets relay battery, talk battery, ring voltage. It will be a project. Does this operate on 48v battery as is standard with common-battery COs? Also does it need ground start CO trunk, or will it work on off-hook start trunk? To summarize, if I have this right: Station to station: * Rear plug to calling station * Push front key to locking position, talk to associated cord set (calling station) * Front plug to called station * Pull front key to momentary position, ringing voltage to front plug Trunk to station: * Front plug to calling trunk * Push front key to locking position, talk to associated cord set (calling trunk) * Rear plug to called station * Pull rear key to momentary position, ringing voltage to rear plug Why is it that on station-to-station, called party gets front plug, but on trunk-to-station, called party gets rear plug? Why not both the same? Or do I have something confused? I would love to see a photo of original instructions that are on your board ... my board is all jacks, with no room for any printed material. I'm a little unclear. If you get an incoming trunk call, and insert front plug to calling trunk jack, does that immediately seize the trunk? Or is the trunk NOT seized until you push the front key to locking (talking) position? Also, I assume this is all bridged ringing since it would be used within a local building or group of buildings. Thanks a million for this outstanding video! (and 73 from K3GEM, if you happen to be a ham)
Only one DC battery supply is required for talking and relay operation, but it is 24 volts instead of 48. Certain old telephone key system power supplies work well for this switchboard application, such as the Western Electric 20B2 that I am using. It supplies both the DC voltage and the AC ringing voltage. There is one currently available on Ebay, but they are asking about $150.00. Power is connected to terminals on the MISC Terminal Strip. On mine, the negative 24 volt battery is connected to terminal 1; the positive ground is connected to terminal 45; the AC ringing generator +/- is connected to terminal 27 and the generator return is connected to terminal 35. The trunk circuit tip and ring wires connect directly to the 2 wires of my residence landline, which is a regular loop start line. You are correct on your procedures for the two types of calls. The internal wiring of the cord circuit is not exactly the same for the front and rear cords. I believes some supervisory functionality may be lost if a rear cord is plugged into a trunk circuit. I can send you a photo of a copy of the printed card instructions that I found in one of the switchboard Equipment Drawings. Just post your email address in a reply to this comment. On an incoming call, the trunk is seized by the far end Central Office when it completes its connection to the switchboard telephone number and sends ringing current towards the switchboard. The seizure is indicated to the operator by the lighting of the trunk lamp. When the font cord is plugged into the trunk, it stops the ringing from the Central Office. Pushing the front cord key to the TALK position establishes the talk path. The operator is instructed to push this key before plugging into the trunk to avoid any "dead" air to the caller. The telephone stations are wired with their ringers bridged across the tip and ring wires in the same manner as single party residence telephone sets. I'm not sure if that's what you meant by "bridged ringing". I hope this answers your questions satisfactorily. Good luck with your project and thanks for watching.
I 'operated' one of these in the early 70's - and seeing it again in this video was like meeting an old friend!! I also had the joy of operating the paper punch Telex 'machine' and the Gestetner wax stencil duplicator, you don't have those lying around too do you?
I'm glad the video rekindled some good memories for you. Unfortunately, I don't have any of the other apparatus you mentioned. I imagine those items would bring back both some good and some frustrating memories.
Me too, Susan! Early 70's. But it wasn't exactly like this one. It's been over almost 50 years ago. Hard to remember exactly what it was like, but it seems the cords on my PBX were side by side. And there were buttons to push instead of the levers to make extension phones ring. I also remember the wax stencil duplicator, but I don't remember ever operating it. Just seen it done. (Edit - Oh, just saw below that it was probably a 555 that I worked on.)
Just search on "Ernestine" in RU-vid and a number of the Lily Tomlin videos will show up. You can get a good look at her 555 switchboard with its side by side cords.
The connection to the 551A is via the MISC Terminal Strip in the back of the unit. The particular terminals to connect is variable based on the options installed. On mine, the negative 24 volt battery is connected to terminal 1; the positive ground is connected to terminal 45; the AC ringing generator is connected to terminal 27 and the generator return is connected to terminal 35.
Thanks for the wonderful demo. What happens when a caller from an outside trunk hangs up but the station party is still off hook? Does the supervisory light let you know that the outside party has hung up? Not sure if this would work considering it’s a connection from an outside office.
Timestamps: 0:30 History 2:54 Overview of the face panel 18:42 Inside the rear of the switchboard 25:15 How to operate the switchboard One question, why would someone buzz the operator for a three way call during an active phonecall?
There was no distinction in how they were used or in how they performed. Their circuitry was exactly the same. The color difference was a visual aid for the operator when the switchboard was very busy and there was a mangle of criss-crossed cords and plugs across the face of the board. When a call ended and the cord supervisory lamps came on, a pair of lit red lamps would let the operator know that she/he had to trace out a pair of red cords with her/his hands and eyes and disconnect two red plugs, and vice-versa if the two lit lamps were white.
What the moderator didn't tell us is what happens should the outside party hangs up first. Would the central office send a disconnect signal that activates the supervisory lamp for the cord connected to the trunk?
No, there are no disconnect signals provided by the trunk circuits. The PBX operator will only be aware of a disconnected call when the supervisory lamp associated with the PBX station lights up when that station hangs up the phone.
the battery you mention, I assume it's to keep the calls working if the power goes out? the voice and tones are powered by dc, so easy to power them from a battery, but the ringer is ac so was a difficult thing to run from a battery back then.
Both the ringing current and battery were usually provided over cable pairs from the telco central office. This supply was not affected by a local utility power failure. However, the battery supply may not have been adequate for PBX's that had a long loop to the central office, and so a local battery was provided, generally locally charged through a rectifier. If the supply from the central office was disrupted, the local battery would handle everything but the ringing, which was handled by the manually operated magneto. Of course, a cable disruption would also affect the ability to handle incoming and outgoing calls.
@@Hicken65 that's some interesting insight, thank you. the phone companies are in the business of communication, not so much power distribution. that's a job for the utility company. makes sense. things like that are still done today. land lines are slowly going away, but in coming years we'll see more and more power over ethernet (PoE). you have a central switch in the building that provides power to devices over the communication lines. it kinda scares me, how much power the new tech tries to push over a wire that was only intended for communication. these wires are thin today. were the telephone wires back then all copper?
@@lorenzo42p Yes. The cables from subscribers premises to the central office are twisted pair copper, typically in 22 to 26 wire gauge depending on distance from the CO.
Excellent video! I've always wondered how to operate this switchboard. I remember this type in old hotels. I have one question. the back row of switches: It was used to answer a ringing trunk line. You used the front jack to access the trunk line and then pushed the back row switch away from you to all the attendant to speak with the incoming trunk caller. Is there any occasion where that back row switch is pulled toward the attendant? In the front row switch, this causes a ringing signal to the station to which it is connected. But, I didn't see any reference to pulling the back row switch toward the attendant. Finally, does the attendant have the ability to speak to only one of the parties on a connected call, or when she pushes the front row switch to the rear, and connects to the line, it's always a 3-way conversation? Thanks! Fascinating stuff! Thanks for posting this!
I think you are having some confusion regarding the key rows. The row closest to the operator is the front row and the row closest to the vertical face panel of the switchboard is the back row. The operator always pushes the front key backwards to its locking position to talk to a subscriber. An incoming trunk call is answered by inserting a front cord into a trunk jack and pushing back on the front key to enable the operator to talk to the incoming caller. The back row cord is plugged into the called station jack and the back row key is pulled forward to ring the called station on this incoming call. On a station to station call, the front key of the cord circuit is pulled forward to ring the called station (see starting at 29:28 on the video). On a connected call, if the operator pushes back on the front talk key, there will always be a 3-way conversation. Splitting was available on many types of switchboards, but not the 551A. I hope this answers your questions and thanks for watching.
@@Hicken65 It does, thank you. It is the case of an incoming trunk call that once connected to the station, the back key is pulled in order to ring the station. That makes sense. Again, very interesting. I saw another video where there was a challenge to a board operator to handle multiple calls as fast as he could. It was great to watch! There is a movie on Amazon Prime, "The Vast of the Night." I was so-so on the movie, but there was quite a bit of manual switchboard stuff going on. I noted that once the called station was connected by cord, the ringing was done by the attendant pushing one button, and then she just flipped a lever up to disconnect her voice from the line. She moved on to the next call. Apparently, the ringing was automatic after that. Thanks, again! Chuck Gage
@@cggage Glad to be of help. I have a number of other telephony videos that you may be interested in. Just search my channel name, Hicken65, on You Tube.
a light will turn on. Basically, if the operator needs to do anything there is a light. If everyone is connected then there are no lights. That's what I understood.
The two wires from each of the maximum of 40 stations are connected to one side of the right hand terminal strip in the rear of the switchboard. The 40 pairs of internal wiring from the other side of this terminal strip are cabled to the 40 station jacks and lamps.
Awesome video and I learned a lot. I am going to try and bid on a switchboard on a local online auction here in Michigan and you answered a lot of questions that I had. I take it you had a career with a telephone company?
How about for the old Kellogg wall box telephone with the long speaker and the receiver on the switch hook on the left and the magneto on the right? Would that work for this type of unit?
No. The 551A switchboard only works with manual telephones designed for common battery operation and without magnetos. Magneto telephone sets worked with much earlier designed magneto drop shutter switchboards.
@@Steinninn Unfortunately, I do not have a magneto switchboard. However there is an excellent description online here; www.gutenberg.org/files/15617/15617-h/15617-h.htm Go to Chapter XXI.
