I know Im randomly asking but does any of you know of a method to log back into an Instagram account? I stupidly lost the account password. I would love any help you can offer me.
I'm Sarah and I say we need to use the whole thing :) Best attitude for a museum, run it all and demonstrate it ALL! That panel switch is an amazing machine, they were so lucky to have been able to save it!
Cool video Sarah, thanks! I worked for Bell Canada...we changed X-Bar and a Step Office to Nortel DMS-100 in one exchange in the city of Windsor, over the course of three weeks and every week I went down to check progress, it got quieter and quieter until the total cutover... I just heard cooling fans and no switches. Very eerie...and it was the end of an era. Thanks to a museum like yours, we won't forget. Sad, as these switches were pretty reliable for how they were made. Real workhorses!
Hi Kevin, I was on test board as well! I will never forget the: CALRS> Prompt. ESS came in when custom calling features came, then we logged right into the DMS itself. I remember seeing CPB on my buddies line and saying just testing the line lol...
There is so much architecture that was designed in such a thoughtful and solid manner. It is mind blowing to think this was all achieved mechanically with motors, electromagnets, and wires. In many ways it reminds me of how computers work, only you can see this machine in action. You can’t really see what a computer is doing. That’s what is so jaw dropping about it. It was invented so long shop by some very brilliant people. The Leonardo DaVinci of telephone switches people. Not many people could have figured this out. They were special people.
You will have to look at an electro-mechanical computer built from relays. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-vVgc8ksstyg.html ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-_j544ELauus.html ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-n3wPBcmSb2U.html
Can anybody explain how a telephony anomaly that i was part of (back in the late 1970s or early 1980s) could have happened? When I was much younger, our rural communities were served by the small, independent Red Hook Telephone Company in upstate Dutchess County, NY (sold first to Continental, then to Frontier, as best as I can recall). One evening, I picked up the phone to find many other people already in conversation. Apparently, anybody that went off hook was just joined together in one big "party line" scenario. This party was well under way before I joined and overall lasted at least several hours. Folks just dropped in and out just by picking up their receivers. (I have friends who still recall that day, so it wasn't just the fevered dream of a young telephone phreak.) I'd been in the CO a few years before and at that time they had an ancient frame type system - lots of moving parts. I'm not sure if that was still in place when this event occured. Any ideas how this could have happened and on what type of equipment?
Nice Video. Good job. I'm a long time XB5 Switchman. All I know about a panel switch is they work by magic. However if you need help in wiring a XB5 marker route relay please contact me.
Wow. With this one video you have answered several questions I've never understood since I worked for Ma Bell back in the early 70's. Despite me being the webmaster for TCI, my own BellsyStemPractices.org/ website, and all the switchers I know, I've never gotten an understandable answer as to what exactly a line finder does. It finds the "subscribers line" when their phone goes off hook. I had always pictured it as something to do with locating a trunk line, which didn't make since considering where it is in the circuit. That's something that seems to be so obvious to those in the know, that it never occurs to them to explain that to the layman or museum visitor. I remember seeing those rotary step switches you explained in this video back when I worked in the old materials receiving dock in the Western Electric plant in Arlington VA. I could tell they weren't part of a SxS 'mail box' switch because they were too big. Now I know what they were used for. I could never understand how the vertical cross bar switches worked or what they did before now. I am continually amazed at the geniuses of Bell Labs and Western Electric. Most brilliant folks of their time. Sara is getting much better with her videos. Keep up the good work Sara. You're teaching an old phone nut new things.
@@ConnectionsMuseum So, an operator would look for the lamp or the drop to know which line to plug into. How does the panel switch know where to send the line finder? They're not constantly moving, looking for off-hook telephones, so how do they know where to go? That could be a whole 'nother video.
ssbohio it definitely could be a whole new video. Basically when you go off hook, a special relay that’s in series with your phone line operates. This is called the (L) relay. The (L) relay causes a whole big chain of events to happen, eventually starting a line finder moving upward. It continues upward until it finds battery (-48v) on a special “hunt” terminal on the bank. Once it sees that, it knows that it’s found your line, and stops.
I love your enthusiasm in telephone equipment and your excellent way in describing how it all works, your sense of humor and presentation is just brilliant ! Many thanks for making the videos, they are much appreciated.
Sooo...unless I missed it (very possible) each subscriber is wired across each column in its bank to potentially engage each vertical LF. My mind is still blown how calls are handled in the CO to subscribers in the same CO. How is each subscriber line split when it enters the CO into outbound and inbound routing? It seems there's so much extra copper to handle that and the redundancy that there must be some esoteric DC capacitance and impedance issues.
Yes, the linefinder banks are like a big long sandwich. Each subscriber appears in front of all of the rods (well, half of them in this frame, since its cut in the middle). This way, any line finder can hunt for the subscriber by moving vertically. The subscriber line is split at the MDF when it enters the CO from the outside. Three leads (T,R,S) go to the line finder, and the final frame. The run is so short (only a few hundred feet) that there really aren't too many weird issues. This is how it was done in city manual exchanges for years before the panel switch. Subscriber lines were wired to the "A" board for origination and to the "B" board for termination. What really gets weird is the signaling loop on the trunks between offices. The panel senders use DC signaling to communicate to other offices miles away. (Think like a giant telegraph circuit). So there is a speed limit on that circuit because capacitance and inductance on the wires can make signaling impossible over distances greater than 20 miles or so.
Very cool that there is someone around that still understands some of the older technology of communications. Thank you so much for showing this. Really interesting. I wish I knew you personally. I'd love to see this first hand.
The best part is, Sarah's sharing the knowledge in full extent to the last detail! This will be excellent for curious early telephone buffs who want to build an analog backup system!
For some odd reason I'd really love to work on this gear. That loom wiring is impressive along with Sarah's knowledge. I wouldn't want to be touching it without her help!
Great description. Basically this line finder is a processor built using binary logic and do-while-loops, processing input bits and pulses according to state machines, along with some timers, driving output bits and pulses. Quite fundamental yet when you stack everything up it is an extremely complex system.
So the rotary switch is doing a round-robin type operation to spread the workload over all of the line finders. Sarah, your fascination with the technology and how all the equipment works is quite palatable and wonderfully infectious!
this seems so archaic compared to today digital switch. still love it from where we came from when phones still relayed on maniacal systems to connect calls
So what were the constraints on these - like does that mean the total number of subscribers who could make phone calls at once is the quantity of rods that exist in the selector? That seems like a really tiny number of rods to select calls for 300 subscribers?
I can’t wrap my mind around how much physical space a phone call used to take. Are the subscribers wire hooked up to more than one line finder poll? So if one was in use a different poll would activate? Or would everyone wired to the same poll just need to wait for someone else to finish their call?
Line finders in Step use a similar concept with a line relay that triggers a selector to start moving, but uses step switches (with a special set of contacts for vertical hunting) instead of panel selectors.
When you pick up your phone, battery (-48V) is placed on one of the terminals corresponding to your line. When the brush touches that terminal, a relay operates, which stops the upward motion of the brush. Then the battery is removed from the terminal for the rest of the call.
There is also a common trigger circuit that basically says "Someone within this line finder needs a connection." This is operated by the line relay, and the cutoff relay prevents it from being constantly powered. A similar system is found in Step, not sure about XB. There's a good video about line finders in Step that explains how the system works, but I don't remember the title.
Love your videos Sarah, you are awesome!! Question: How does the line finder detect an off-hook condition? An off-hook condition applies a short between the tip and ring (48v and Gnd.) so the line finder has to detect this condition somehow. I installed ESS equipment for Western Electric. Ferrod sensors were scanned to detect off-hook in the line switch frame, but this thing obviously had its own thing. Thanks
Well, its almost like a ferrod sensor, but more low-tech. Every subscriber has their very own pair of (L) and (CO) relays. The (L)ine relay is in series with your phone, so when the off-hook short happens, it operates the (L) relay. When the line finder has found your line, the (L) relay releases, and the (CO) relay operates which grounds your sleeve lead so your line is marked busy to anyone who tries to call it.
Check the replies to the old comments, Sarah replied there! :) I was very curious too. Basically there is a relay (in line) on every line that is triggered when you go off hook, that relay is what starts it all.
This is so interesting, I'm so glad of having found this channel. I knew nothing about how telephone networks worked, old or new, and now I'm glued to those videos.
2:56 I would like to know why there's a twin-lens reflex camera mounted sideways to the panel, just to the right of the dial and below the ammeter. It is pointing to the right and doesn't look as if it could photograph anything, since most TLRs wouldn't focus closer than 1 meter.
The point of a line finder is economy of scale, but you wonder how much economy of scale they are really getting by adding all these flip-overs and special logic and ... Are they all controlled in common? So there's only one logic circuit that selects one line at a time, using whichever rod is available but only one at a time until that one is done and then finding the next call with a different rod?
@@ConnectionsMuseum The split line finder is just 2 line finders in one big package, as I understand it, so I'd still call it 1 control circuit per line finder. I was wondering if there were "race conditions" where two selectors could find the same line at the same time, or something like that - but if there's only one control circuit, that can't happen.
I'm curious, what happens if you go off hook and there are no selectors on the linefinder available? (We were served out of a step office when I was growing up, and that never seemed like it was an issue in stepworld...)
I'm a year late but I remember another museum showing off an "equipment busy" tone. I imagine if the company you used had one of those tone generators this would be the situation where that tone would play.
![[Panel] How does the line finder work?](/img/logo.svg){kind=logo}
