Hi Forum,
I recently acquired an old hotel switchboard made by Brazilian Ericsson ("Ericsson do Brasil"). I emailed a message about it to the Singing Wires mailing list. People there were very helpful with information, but no one had any specific knowledge about the particular machine, so I'm posting here too - sorry to anyone who is seeing this information twice.
I'm hoping to restore this machine and if anyone has any specific information about its history, parts or even circuit diagrams, please let me know. I have seen another floor-standing model for sale here in Brazil that had an integral wooden base. I also saw a photo of an near identical unit, albeit with configured differently, from a hotel in Mexico.
From a suggestion on the Singing Wires list, I had a look at one of the lamps which had a voltage rating marked of 24V. Someone there thought that the lamp may be of American origin rather than European. Perhaps it was assembled in Brazil using components from various sources. Please see the photos attached.
While I'll be doing some of the simpler restoring tasks myself (rewiring the patch cords and hand-piece, cleaning, etc), I'm currently looking for a technician to assist with the electronic side of things.
Please reply to this thread if you have information on the machine or any suggestions.
All the best!
Quote from: escuta on July 28, 2017, 10:47:50 AM
From a suggestion on the Singing Wires list, I had a look at one of the lamps which had a voltage rating marked of 24V. Someone there thought that the lamp may be of American origin rather than European.
The lamp in the photo is marked "Philips". I'm pretty sure Philips did not mfr lamps in the US. GE, Chicago Miniature and Sylvania as well as AT&T's Western Electric were the US mfrs. Philips did own Dialco (originally "dial light company"), a mfr of pilot light socket assemblies used primarily in radio and other electronic equipment but I'm quite sure no lamps were mfd under that name either. I don't know the history of Philips' acquisition of Dialco.
You might find an article in the "Ericsson Review" describing this switchboard. I believe there is an archive on line on L. M. Ericsson of Sweden's site.
The information stamped next to "tipo" and "no." on the ID plate in your photo do not seem to be legible. If you can read them when directly viewed I suggest posting this information here. It may facilitate finding documents or an Ericsson Review article. Searching purely based on description would be too time consuming.
The inscription on the lamp clearly identifies the manufacturer as Philips NV. Philips was an early and still is a major lighting equipment maker in Amsterdam. So, it seems logical that this switchboard was equipped with European parts. I think, that an American switchboard would most likely use General Electric, Sylvania, or Western Electric lamps. Some switchboard makers, such as Kellogg S. & S. Co even made their own lamps.
Selection of the right kind of lamp for your board probably depends on the design of the supervisory circuits. If the lamp current is switched with a line relay, its resistance is perhaps less critical, as when the lamp is directly inline with the station.
Since you have a lamp, have you measured its cold resistance ?
Are there any type numbers on that type tag ?
BTW, a switchboard is not a machine. I find that characterization rather distracting. It's all manual work to make this equipment work.
A step-by-step switching system could be called a machine.
By the type of wood work in this unit, I think that it may have been made middle-1930s to ~1950 perhaps.
Quote from: unbeldi on July 28, 2017, 12:32:15 PM
The inscription on the lamp clearly identifies the manufacturer as Philips NV.
...
Selection of the right kind of lamp for your board probably depends on the design of the supervisory circuits. If the lamp current is switched with a line relay, its resistance is perhaps less critical, as when the lamp is directly inline with the station.
...
BTW, a switchboard is not a machine. I find that characterization rather distracting. It's all manual work to make this equipment work.
A step-by-step switching system could be called a machine.
Ah! Could not make out the "NV" although I'm familiar with their full name.
From the rear photo, it does not seem that there are enough relays in the unit for there to be line relays, probably just cord circuit relays. Even much larger PBXs such as WE 551 and 555 did not use line relays except when added individually for specific off-premises extensions.
Panel and Crossbar (XB) exchanges were also referred to as "machines", no stretch at all for Panel and not too much of a stretch for XB. In fact the Bell System originally used the term "machine switching" rather than "automatic" or "dial" to refer to what generally became known as dial service. Funny but with the evolution to ESS with stored program control and even digital ESS with no relays to speak of, the term "machine" continued to be used. Old habits die hard.
Quote from: Alex G. Bell on July 28, 2017, 01:05:09 PM
Ah! Could not make out the "NV" although I'm familiar with their full name.
Oh, I just used the NV without reference to the actual inscription on the lamp. I am not sure what it is that follow the mark "PHILIPS" on that lamp.
Quote
From the rear photo, it does not seem that there are enough relays in the unit for there to be line relays, probably just cord circuit relays. Even much larger PBXs such as WE 551 and 555 did not use line relays except when added individually for specific off-premises extensions.
I suspect so also, the board is rather small, and it is not likely that it was made for stations to be so far away that it would require line relays.
From the small Kellogg cordless boards I know that they equipped only the 20-station boards with line relays, not the smaller ones.
Quote
Panel and Crossbar (XB) exchanges were also referred to as "machines", no stretch at all for Panel and not too much of a stretch for XB. In fact the Bell System originally used the term "machine switching" rather than "automatic" or "dial" to refer to what generally became known as dial service. Funny but with the evolution to ESS with stored program control and even digital ESS with no relays to speak of, the term "machine" continued to be used. Old habits die hard.
Agreed. One might however say, that this switchboard contains
simple machines, which are devices, like the levers of keys, that transform energy in a very basic manner.
Originally,
machines transformed energy into mechanical energy, but it has been extended to electronic devices, such as computers even.
Quote from: unbeldi on July 28, 2017, 02:02:30 PM
From the small Kellogg cordless boards I know that they equipped only the 20-station boards with line relays, not the smaller ones.
Probably also a function of the intended operating voltage range. They may have included line relays to permit operation over a wider range including lower voltages.
Quote
Agreed. One might however say, that this switchboard contains simple machines, which are devices, like the levers of keys, that transform energy in a very basic manner.
Originally, machines transformed energy into mechanical energy, but it has been extended to electronic devices, such as computers even.
That always seemed to me like a stretch to the breaking point. As I see it, just because the disk drives are machines that does not make the whole thing a machine. It's principle function is computation which does not employ mechanical devices, which just provide storage. I'd make the same case for a manual swbd.
Quote from: Alex G. Bell on July 28, 2017, 02:13:00 PM
That always seemed to me like a stretch to the breaking point. As I see it, just because the disk drives are machines that does not make the whole thing a machine. It's principle function is computation which does not employ mechanical devices, which just provide storage. I'd make the same case for a manual swbd.
I have lingering objection to that inclusion myself, and I don't promote the term for computers myself, but have come to accept it.
Quote from: unbeldi on July 28, 2017, 02:19:26 PM
I have lingering objection to that inclusion myself, and I don't promote the term for computers myself, but have come to accept it.
Yes, a few years after publication of "The Soul of a New Machine" I stopped bristling at mention of the title. ;D It just was not worth the emotional energy!
Quote from: unbeldi on July 28, 2017, 02:02:30 PM
Oh, I just used the NV without reference to the actual inscription on the lamp. I am not sure what it is that follow the mark "PHILIPS" on that lamp.
Seems "IMP." is an abbreviation but what comes after that, the font does not match.
Quote from: TelePlay on July 28, 2017, 02:38:25 PM
Seems "IMP." is an abbreviation but what comes after that, the font does not match.
Yes, "IMP" might be a reference to a version with reduced size from the standard. Time for the OP to read the lamp and the ID plate and tell us what they say. No point spending more time guessing and speculating.
Thanks Alex G. Bell and unbeldi. That Ericsson Brazil plaque unfortunately has the type and number fields left blank. On the lamp, from memory (I put the lamp back in the switchboard), the figures following "IMP." (imperial?) look like "AA" but with the crossbar of the first "A" missing. Tomorrow I'll have a chance to remove another bulb. If I can I'll attempt to retrieve a different lamp to see if the stamp is any clearer. Thanks for the tip on the Ericsson review. I did find a list of them on the following page, however the links appear not to open the PDFs on the Ericsson site:
http://runeberg.org/ereview/
Are you aware of an current online source of the reviews?
I have some more photos, will post some in this post and some more in another.
some more...
I believe this board should actually be wall-mounted, correct?
How else would the cords be able to retract properly ?
I think the design with rounded corners may have been a post-WWII design in Sweden.
In the US, I think it was only Kellogg that did that, but they started building in the style in the 1930s. Stromberg-Carlson boards were still more "sharp-edged", and AE and WECo had even more-old-fashioned designs.
I think this timing is also supported by the style of screws, etc.
Quote from: escuta on July 28, 2017, 03:38:15 PM
Thanks Alex G. Bell and unbeldi. That Ericsson Brazil plaque unfortunately has the type and number fields left blank.
Too bad. However LME was pretty consistent about using uniform letter prefixes (defined by themselves) before their model #s, such as "ARD" for crossbar exchanges. There's probably some (currently unknown) prefix for cord swbds and once we determine what it is, knowing it may facilitate finding a specific article.
Quote
On the lamp, from memory (I put the lamp back in the switchboard), the figures following "IMP." (imperial?) look like "AA" but with the crossbar of the first "A" missing.
In other words an upside down "V". I don't know what that means but perhaps a search for Philips switchboard lamp catalogs will turn something up.
Quote
Tomorrow I'll have a chance to remove another bulb. If I can I'll attempt to retrieve a different lamp to see if the stamp is any clearer. Thanks for the tip on the Ericsson review. I did find a list of them on the following page, however the links appear not to open the PDFs on the Ericsson site:
http://runeberg.org/ereview/
Are you aware of an current online source of the reviews?
I have some more photos, will post some in this post and some more in another.
You're welcome. I've never encountered the runeberg.org site before. At one time the magazine itself was on the LME site but I have not looked at it in a few years and have migrated PCs without migrating bookmarks so I may or may not have the URL I used in the past.
The articles might still be on the LME site but with a minor reorganization of the site, the exact path could change rendering them all invalid. I suggest trying to explore the LME site by navigating back towards the home page from one of the links contained in the Runenberg.org page. That might not lead anywhere but it also might lead you to the archive.
I may have an LME E-R article index from the time when I accessed the LME E-R archive but cannot spend time looking for it at this moment. I think I also have a cache of British Ericsson articles. It's certainly possible they sold this swbd in multiple countries and that there's an article about it among them but again I cannot spend the time right now.
Quote from: unbeldi on July 28, 2017, 03:57:31 PM
I believe this board should actually be wall-mounted, correct?
How else would the cords be able to retract properly ?
There were special tables for small swbds with a hole in the top for cords to hang through.
Quote from: unbeldi on July 28, 2017, 02:02:30 PM
From the small Kellogg cordless boards I know that they equipped only the 20-station boards with line relays, not the smaller ones.
Another possible reason for using line relays in the Kellogg board might have been that it was competing with WE 506-type cordless PBXs which used magnetic signals and as a matter of "specsmanship" (being able to state that it has the same operating range as the 506) relays were required to match the loop range of the 506.
It's also possible that at that time only carbon filament lamps were being made, which are less efficient than tungsten lamps used as line lamps in all cord swbds I know of which do not have line relays. Carbon filament lamps probably have an even lower loop resistance range.
Quote from: unbeldi on July 28, 2017, 03:57:31 PM
I think the design with rounded corners may have been a post-WWII design in Sweden.
The white nylon relay coil front spool header and molded phenolic terminal blocks also suggest pretty late mfr, quite possibly 1950s or 60s.
Here a photo of a nicer looking freestanding version that was on sale here some time ago (more expensive than I could afford) and a second unit from Mexico. Yes, mine has a bracket at the back for wall-mounting
Quote from: escuta on July 28, 2017, 04:16:55 PM
Here a photo of a nicer looking freestanding version that was on sale here some time ago (more expensive than I could afford) and a second unit from Mexico. Yes, mine has a bracket at the back for wall-mounting
Funny how the dial seems to be cobbled onto both of them, as though not provided for in the original design.
The second one is also equipped with a US payphone handset with metal armored cord. The blue grommet on the bottom identifies it as being "hearing aid compatible", for compliance with the US ADA. Hearing aid compatibility requires the receiver unit to emit a magnetic field for pickup by the hearing aid for clearer coupling of the received speech than would be possible acoustically.
I found your switchboard, I believe.
In 1946 and 1950, Erik Iengqvist published two articles in Ericsson Review introducing a new series of manual switchboards.
The 1946 paper deals with local battery systems, while the 1950 paper extends the design to common battery operation.
ER 1946 v23(3) p250, New Series of Manual LB Switchboards with Cords
ER 1950 v27(2) p36, Manual Private Branch Switchboards with Cords
I have attached both articles. Your board is of course in the second article, since it is a common battery switchboard. The article also shows the dial attached in the same location. One difference I see, is that your board does not appear to have the hand generator, but perhaps I only missed it.
That's amazing unbeldi, thank you very much! I'll have a good read through these tomorrow. Mine does have a hand generator positioned on the right hand side. The dial however, doesn't seem to be what looks like a Bakelite dial in the original though. I'll be back with more questions, no doubt. I really appreciate your help!
Quote from: escuta on July 28, 2017, 05:38:15 PM
That's amazing unbeldi, thank you very much! I'll have a good read through these tomorrow. Mine does have a hand generator positioned on the right hand side. The dial however, doesn't seem to be what looks like a Bakelite dial in the original though. I'll be back with more questions, no doubt. I really appreciate your help!
Ah, in your new pictures I do spot the generator now, in a view of the inside. It is a characteristic Ericsson design and uses Alnico magnets, that Ericsson first introduced in the late 1930s. Somewhere I have that article too, I researched Ericsson hand generators before.
Quote from: unbeldi on July 28, 2017, 05:18:07 PM
I found your switchboard, I believe.
ER 1946 v23(3) p250, New Series of Manual LB Switchboards with Cords
ER 1950 v27(2) p36, Manual Private Branch Switchboards with Cords
I have attached both articles.
Did you find an entry point to the LME E-R archive with an index or find them somewhere else?
Quote from: Alex G. Bell on July 28, 2017, 05:47:15 PM
Did you find an entry point to the LME E-R archive with an index or find them somewhere else?
I have an archive of most of ER 1924—2000 on my local disk for which I created a full-text search index.
Quote from: unbeldi on July 28, 2017, 05:59:49 PM
I have an archive of most of ER 1924—2000 on my local disk for which I created a full-text search index.
Ah!
Located the Ericsson Review page on the Ericsson website. It's here:
https://www.ericsson.com/en/about-us/history/sources/lme-review
And found a closer match for my board, the ADE 1210 from 1953 which is identical, however mine has a jack socket between the "S" (splitting key) button and the "~" (pole changer key) on the vertical panel. Not sure what this would be for.
Have attached a jpeg and 2 pages from ther 1953 PDF.
Cheers
Quote from: escuta on July 29, 2017, 09:46:14 AM
Located the Ericsson Review page on the Ericsson website. It's here:
https://www.ericsson.com/en/about-us/history/sources/lme-review
And found a closer match for my board, the ADE 1210 from 1953 which is identical, however mine has a jack socket between the "S" (splitting key) button and the "~" (pole changer key) on the vertical panel. Not sure what this would be for.
Have attached a jpeg and 2 pages from ther 1953 PDF.
Cheers
I don't see why you think it is a closer match. That board is from the same model line and only the article is from 1953, not necessarily the board. The article is an overview article of Ericsson's line of intercommunication systems.
The model line contained many versions with varying capacity and special features. The 1210 has 10 cord circuits, while yours has only eight cord circuits, the same as in the original paper of 1950, showing the 1205.
For reference:
ER 1953 v30(1) p13, O. Siewert,
Modern Telephone Systems for Internal Communications
Mine has 10 slots for cord circuits, it's just that only 8 have been installed. Also the hook for the receiver is identical on the 1210 as is the location of the socket for the receiver cord. Yes, you're correct it may not be from 1953 but to me the 1210 looks the most similar.
Quote from: escuta on July 29, 2017, 10:24:13 AM
Mine has 10 slots for cord circuits, it's just that only 8 have been installed. Also the hook for the receiver is identical on the 1210 as is the location of the socket for the receiver cord. Yes, you're correct it may not be from 1953 but to me the 1210 looks the most similar.
Is the ID plate shown in #7 the same one which appears at the upper right in #11 or are there two, one internal and one external?
In #15 (bottom view of key shelf) is there really space for two more cord assemblies between the furthest right and left cord units and the outer wall of the frame, which appears to be molded from black plastic? It's hard to tell due to the perspective resulting from the camera being so close to the subject. The fact that there are two blank plates on the top of the keyshelf does not necessarily mean 2 more cord circuit assemblies could be added. Each cord circuit requires at least one relay, inductors or transformers ("repeat coils") mounted on the framework. There may not be sufficient space for the parts required to support the cord & key assembly even if there is sufficient space for the keys and cords themselves.
A puzzling statement in the E-R article: "The telephone instruments ... are either normal C.B. instruments or, if the lines are short, instruments of the domestic type". I suppose by "domestic type" they really mean
internal type, i.e. series talking circuit type. This seems to probably be a mis-translation from the Swedish.
It's too bad the quality of the PDF is so poor. The text contains obvious JPG compression artifacts, appearing as speckles surrounding the text, from using too high a compression level. I may have an original of this issue of the publication and may be able to scan it in the future, but not in the near future.
No, there is only one name plate which is on the inside of the door. Yes, I think there is space for two more cord circuits, one to the left and one to the right. Please see the attached photo.
Also just found this link for an ABH 162, which seems to have a jack between the "S" button and the "~" selector:
http://telefoniemuseum.nl/Oude%20centrales/BB%20wandpost%20Ericsson%20ABH%20162.htm
Quote from: escuta on July 29, 2017, 04:17:21 PM
No, there is only one name plate which is on the inside of the door. Yes, I think there is space for two more cord circuits, one to the left and one to the right. Please see the attached photo.
OK, but I'm still skeptical about which E-R article is applicable. Most of the descriptions in the 1953 article you found refer to internal systems. The text for the AD1210 makes no mention of the connection of exchange lines and talks about 50-station capacity. It would not be expandable to 50 stations if an exchange line strip were installed. OTOH the dial shown in the photo would serve no purpose in an isolated purely internal system.
The 1950 article OTOH talks about a 40 station + 6 exchange line capacity, making it unquestionably a PBX or "PMBX" as some call it (private manual branch exchange). Your photo shows a strip at the top with alternating light and dark lamp caps, suggesting probably exchange line jacks, and that yours is a PMBX.
It's also possible there is no essential difference between the isolated model discussed in your 1953 article and the PMBX version discussed in the 1950 article, that they are just different configurations of the same equipment.
Quote from: escuta on July 29, 2017, 09:46:14 AM
Located the Ericsson Review page on the Ericsson website. It's here:
https://www.ericsson.com/en/about-us/history/sources/lme-review
And found a closer match for my board, the ADE 1210 from 1953 which is identical, however mine has a jack socket between the "S" (splitting key) button and the "~" (pole changer key) on the vertical panel. Not sure what this would be for.
One possible purpose for this additional jack would be to plug in a second handset so that a supervisor training a new operator could also talk and listen at the same time as the trainee. Most PBX switchboards have jacks for two headsets/handsets for this purpose. Locating it on the face would make its use more convenient than on the side with the main jack.
The 1953 article is simply a review of all intercommunication systems of the time. It does not introduce any particular system.
It is the 1946 and 1950 articles that introduce the line. The 1950 article presents the design criteria for the CB model line, and for the 1953 article they just picked one of the CB variants, perhaps the best selling type, or the latest variant. It would be a mistake to read any thing more into that.
If you were to match by pictures, then you have neither of those boards, since yours only has 20 extensions. They may even had variants with and without line relays, so you can't even go by counting components from a picture.
The fact that the handset cradle is different is a minor aspect. It could even be an ordering option, or a local preference for the Brazil models.
I would recommend to you to document your board by the components that are in fact installed, broken down to each functionality. Identify as many components as possible, for example I noticed the series of relays (RCA) used, etc. Relays are often subject to evolution of materials used. There is documentation available for many of the Ericsson parts. I think I have lists of relays with switch configurations and other components.
Switchboards were also often built for specific customers with requested configurations and specifications, so a general magazine article may not cover all that. The introductory articles by the equipment design engineers also don't always match the exact parts or features that end up in production. Again, it is best to document what you have and relate that to documentation.
QuoteThe 1950 article OTOH talks about a 40 station + 6 exchange line capacity, making it unquestionably a PBX or "PMBX" as some call it (private manual branch exchange). Your photo shows a strip at the top with alternating light and dark lamp caps, suggesting probably exchange line jacks, and that yours is a PMBX.
On this top strip there are 10 jacks but only five with lamps (or at least with light coloured caps). Above each of these is a label with what looks like a telephone number, the first of which is "222_5822". The rest all start with 222.
Quote from: escuta on July 29, 2017, 05:41:47 PM
On this top strip there are 10 jacks but only five with lamps (or at least with light coloured caps). Above each of these is a label with what looks like a telephone number, the first of which is "222_5822". The rest all start with 222.
Almost certainly those are exchange line numbers and jacks and there is only enough internal space for 5 of the relays required for each exchange line to detect incoming ringing, so 5 of the lamp sockets are blanked.
When I change the gamma on your photo #17 to 2.5 I see only 5 pairs of equipment, so most likely alternate jack and lamp holes are not equipped with contacts. This is consistent with the E-R article stating a capacity of 6, though where the 6th would fit is TBD.
Photo #16 shows an R1 (functional designation) relay, one of 5, with the cover off, shown in #2 and #17 with the covers on. These are probably the 5 ringing detection relays for the 5 exchange lines. You could confirm this by tracing the wiring harnesses (bundled wires) to see whether there is a branch from these 5 relays to the top jack and lamp strip. Most likely all 5 relays are designated R1 because each serves the same purpose for a different exchange line "trunk" jack and lamp circuit.
Quote from: unbeldi on July 29, 2017, 05:37:53 PM
I would recommend to you to document your board by the components that are in fact installed, broken down to each functionality. Identify as many components as possible, for example I noticed the series of relays (RCA) used, etc. Relays are often subject to evolution of materials used. There is documentation available for many of the Ericsson parts. I think I have lists of relays with switch configurations and other components.
Yes, thanks, I'll start doing that. These PDFs are going to help in the process.
Quote from: Alex G. Bell on July 29, 2017, 05:49:02 PM
When I change the gamma on your photo #17 to 2.5 I see only 5 pairs of equipment, so most likely alternate jack and lamp holes are not equipped with contacts. This is consistent with the E-R article stating a capacity of 6, though where the 6th would fit is TBD.
When I look, I see that all 10 jacks have contacts and are wired up, it's just that only every second jack unit is coupled with a lamp unit and the non-coupled jacks have only two contacts soldered, to a green and a blue wire. Please the the images attached. #21 shows the back of the top right-hand side of the unit (looking from front) and #22 shows the top-right from the front.
QuotePhoto #16 shows an R1 (functional designation) relay, one of 5, with the cover off, shown in #2 and #17 with the covers on.
Yes that's correct but subsequent relays are labelled R2, R3, R4 and R5 and not R1 (see #23 with all boxes off).
QuoteThese are probably the 5 ringing detection relays for the 5 exchange lines. You could confirm this by tracing the wiring harnesses (bundled wires) to see whether there is a branch from these 5 relays to the top jack and lamp strip.
No, the wiring harnesses from the top jack and lamp strip go only to the top pair of terminal strips in #11 (you can see the wiring harness entering from the left). The terminal strips on the door connect to an external wall-mounted (I understand) "break-out box" to connect with phones, exchanges, power supplies, etc. Fortunately the break-out box was supplied with the switchboard.
There's a few technical things I plan to do with the switchboard this week and I have a few more questions! :
The first task is to reconnect all remaining plugs to the cords. There are 8 plugs remaining but none was connected to any of the cords (they had been removed at some point and stuck back on for cosmetic reasons), so I do not know how to wire them. The cords are 3-core with yellow, black and red wires. Are you aware of any standard colour code used by Ericsson for wiring tip, rim and sleeve on the plugs?
The hand-piece has its cord but has lost the plug that would have attached to the socket seen in photo #1 on the lower left-side of the unit. It has also lost its mic and speaker capsules, see photo #24 with the Bakelite caps removed. The hand-piece cord has three wire, however the socket has 4 terminals. Does this mean that the handpiece is not original? Quite possible, I suppose. Looking at the inside of the socket, one can see that from the left, the 1st, 2nd and 4th terminal are connected to an internal 3-core wire and that the 1st and 3rd terminal are connected by a jumper wire. Can anyone please offer suggestions on how I should go about wiring up replacement hand-piece capsules (I'll try to purchase these today) and connecting the cord to the 4-terminal socket? Would it be possible to find a replacement plug? I'll try using "banana" plugs for testing.
Once these two tasks are done I'd like to try starting up the unit with DC power-supply. I understand that this should be a filtered 24V supply, however I plan to test with a 19V supply that I have handy from an old laptop.
Also, I believe the plugs are 0.206" TRS plugs (photo #5), I have no calipers, but using a ruler it's a bit more than 5mm. Does 0.206" sound correct? They are certainly smaller than 1/4" and modern audio jack plugs are too large to enter the sockets. Would the following plugs make suitable replacements: http://www.markertek.com/product/np3cm-b/neutrik-np3cm-b-trs-206-inch-mil-b-gauge-phone-plug-black-brass
Yet one more question: My unit has no weighted pulleys as shown in the ER articles. I was thinking of try to source something at a sailing/nautical supplies shop. Any suggestions on particular pulley types I should look for, or weights? Other suggestions?
Thanks a lot!
Here is an excerpt of two- and three-conductor plugs of a 1946 catalog for telephone parts.
The second section in this is for three-conductor (TRS) varieties.
The same catalog #648 contains receiver and transmitter elements for a variety of handsets.
You should be able to find the catalogs on the LME history site.
Quote from: escuta on August 01, 2017, 09:45:21 AM
The first task is to reconnect all remaining plugs to the cords. There are 8 plugs remaining but none was connected to any of the cords (they had been removed at some point and stuck back on for cosmetic reasons), so I do not know how to wire them. The cords are 3-core with yellow, black and red wires. Are you aware of any standard colour code used by Ericsson for wiring tip, rim and sleeve on the plugs?
Aside from not knowing the color code LME used for their cords, are the terminals themselves marked with any functional designation? If not electrical tests will be necessary resolve the proper cord circuit cord connections.
First you will need to check continuity of any cord from each of the 3 plug elements (tip, ring and sleeve) to the 3 leads to determine which color is the tip, the ring and the sleeve, the descriptive and formal names of the 3 plug elements.
Next, with the DC power disconnected, the DC power input terminals short circuited together, and no TALK keys operated, you should find equal resistance between two of the plug cord terminals for any given cord circuit and the DC power input leads. These would be the T and R terminals since a talking circuit must be balanced electrically and therefore the T must have the same DC resistance to the (+) terminal of the power supply as the R has to the (-) terminal, therefore with the power input shorted the resistances will be equal.
The third should have a different resistance or might test open. This should be the sleeve terminal. It's also possible that two of the terminals will test open and only the third will show continuity if the T&R are isolated in the cord circuit by relay contacts until a plug is inserted and a relay in the cord circuit operates, closing through the T&R.
QuoteThe hand-piece has its cord but has lost the plug that would have attached to the socket seen in photo #1 on the lower left-side of the unit. It has also lost its mic and speaker capsules, see photo #24 with the Bakelite caps removed. The hand-piece cord has three wire, however the socket has 4 terminals. Does this mean that the handpiece is not original? Quite possible, I suppose. Looking at the inside of the socket, one can see that from the left, the 1st, 2nd and 4th terminal are connected to an internal 3-core wire and that the 1st and 3rd terminal are connected by a jumper wire. Can anyone please offer suggestions on how I should go about wiring up replacement hand-piece capsules (I'll try to purchase these today) and connecting the cord to the 4-terminal socket? Would it be possible to find a replacement plug? I'll try using "banana" plugs for testing.
Of course the two which are jumpered together (1st and 3rd) provide the connecting path to the conductor of the handset cord which connects within the handset to both the transmitter and receiver, which given the 3-conductor handset cord must exist.
You will need to determine which terminal at the cord end of the handset is the common, the receiver and transmitter. Perhaps you will be able to determine some of this by visual inspection. Impossible to say without knowing the construction of the handset. If not by visual inspection you will need to perform continuity tests within the handset.
When power is applied to the switchboard there will be a DC voltage between one of the other jack contacts (2nd or 4th) and the 1st & 3rd. This jack contact is the transmitter lead. The remaining jack contact should not have DC on it and would be the receiver jack contact.
You will need to measure the diameter and spacing of the handset jack contacts to determine the characteristics of a compatible plug. It appears from your photo that the left most contact as viewed from the back is spaced further from the other three than the three are from each other. This is done to polarize the plug so it can only be inserted one way (not flipped over 180º).
Polarization is necessary because with 4 operator's telephone jack contacts, a common transmitter and receiver connection between two of them and a common connection within the handset (because of a 3 conductor cord), the common conductor in the handset cord must always be connected to the common circuit in the jack.
It might be expedient for the moment to check for continuity between the contacts of the single jack on the front, which is probably for a supervisor's handset, and the 4 contacts on the side. If they are connected in parallel it may be easier to match the single finger plug at least for the moment. One of the cord circuit plugs might matche that, so one of the cord circuit connecting cords might work for the handset temporarily.
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Once these two tasks are done I'd like to try starting up the unit with DC power-supply. I understand that this should be a filtered 24V supply, however I plan to test with a 19V supply that I have handy from an old laptop.
Also, I believe the plugs are 0.206" TRS plugs (photo #5), I have no calipers, but using a ruler it's a bit more than 5mm. Does 0.206" sound correct? They are certainly smaller than 1/4" and modern audio jack plugs are too large to enter the sockets. Would the following plugs make suitable replacements: http://www.markertek.com/product/np3cm-b/neutrik-np3cm-b-trs-206-inch-mil-b-gauge-phone-plug-black-brass
.206" is a Bell System standard. I don't know whether LME used that size. But 5mm = .196" so if the finger length (spacing of T, R and S) is correct (matches the jack) it may be compatible. However there are probably other sources of American made plugs with tapered switchboard cords already attached so I recommend you hold off on purchasing plugs until later.
QuoteYet one more question: My unit has no weighted pulleys as shown in the ER articles. I was thinking of try to source something at a sailing/nautical supplies shop. Any suggestions on particular pulley types I should look for, or weights? Other suggestions?
Thanks a lot!
Most likely you will be able to obtain proper cord weights from a Bell System switchboard from someone in the US. Lots of switchboards have been scrapped so cord weights are not usually difficult to find. There are a variety of different types of different weights with different numbers of pulleys for long cords which pass through the cord weight twice. I will identify a specific type and post a photo when that's the most urgent next task.
Thanks very much for the detailed information Alex G. Bell and unbeldi, much appreciated. It took me a while to have a good look at the unit - comments follow below:
QuoteFirst you will need to check continuity of any cord from each of the 3 plug elements (tip, ring and sleeve) to the 3 leads to determine which color is the tip, the ring and the sleeve, the descriptive and formal names of the 3 plug elements.
None of the plugs were actually attached when the unit arrived. Most had been yanked off at some point and examining the cord ends, the longest wire in all cases was the black wire, followed by the yellow and then the red. Looking at #28, this suggests that they were connected to tip, ring and sleeve respectively. Examining the other en of the cords each terminates with three terminal rings which allow the cords to be easily snapped into place (#26). The terminal at the tip corresponds to the black wire, the middle is the yellow and the terminal closest to my hand is the red. That seems to match nicely with the idea that black = tip, yellow = ring and red = sleeve. Please correct me if I'm wrong!
QuoteNext, with the DC power disconnected, the DC power input terminals short circuited together, and no TALK keys operated, you should find equal resistance between two of the plug cord terminals for any given cord circuit and the DC power input leads. These would be the T and R terminals since a talking circuit must be balanced electrically and therefore the T must have the same DC resistance to the (+) terminal of the power supply as the R has to the (-) terminal, therefore with the power input shorted the resistances will be equal.
Unfortunately, when I tried this, I discovered that only 3 cord pairs (call and answer) out of the 8 gave any resistance reading at all. They were however consistent. The "black" terminal gave no measurement (ie. the meter stayed at 1), nor did any of the yellow terminals. The red terminals on the call and answer cords (of the 3 pairs that registered anything) all gave a resistance reading.
re. the hand-piece:
QuoteYou will need to determine which terminal at the cord end of the handset is the common, the receiver and transmitter. Perhaps you will be able to determine some of this by visual inspection. Impossible to say without knowing the construction of the handset. If not by visual inspection you will need to perform continuity tests within the handset.
The hand-piece cord has three wires, red black and white. Black is the wire common to the mic (receiver? - sorry I'm new to telephones) and speaker.
QuoteWhen power is applied to the switchboard there will be a DC voltage between one of the other jack contacts (2nd or 4th) and the 1st & 3rd. This jack contact is the transmitter lead. The remaining jack contact should not have DC on it and would be the receiver jack contact.
Using a 19V DC supply, unfortunately I could measure nothing across the terminals in #25
Later, I'll attempt to trace how far the 19V gets in the switchboard.
All the best
Quote from: escuta on August 07, 2017, 10:40:39 AM
Thanks very much for the detailed information Alex G. Bell and unbeldi, much appreciated. It took me a while to have a good look at the unit - comments follow below:
None of the plugs were actually attached when the unit arrived. Most had been yanked off at some point and examining the cord ends, the longest wire in all cases was the black wire, followed by the yellow and then the red. Looking at #28, this suggests that they were connected to tip, ring and sleeve respectively.
That's surprising. North American plugs are internally threaded at the heel and thread onto the thick braided jacket at the plug end of the cord. I'd venture that it would be impossible to rip them off. The braid is so tightly compressed in the threads of the plug that it requires a special tool to grasp the plug and unscrew it from the cord for replacement.
Yes, the length of the conductors must be followed, but reattaching the ring terminals to the leads may be very difficult. If the cord conductors are "tinsel" strands (each strand in each conductor is a flat metal tape wrapped in a helix around an insulating textile core material), special methods are required to prepare the conductor for soldering. I can explain that later.
Do not try to solder the leads directly to the plugs. You must reattach the ring terminals to the leads after first removing them from the plug by removing the screws.
It's hard to determine from #28 whether the lugs were crimped onto the cord conductors or soldered on. If crimped you will have to open the crimp to reuse them. It may be possible to get new ones intended for soldering. These were used in telephone plugs used on US military equipment and sometimes show up on eBay. IIRC, the screw size is ANSI #2. The LME's may be different.
If the conductors are ordinary thread-like strands (unlikely for reliability reasons) it can be soldered directly.
QuoteExamining the other en of the cords each terminates with three terminal rings which allow the cords to be easily snapped into place (#26). The terminal at the tip corresponds to the black wire, the middle is the yellow and the terminal closest to my hand is the red. That seems to match nicely with the idea that black = tip, yellow = ring and red = sleeve. Please correct me if I'm wrong!
This is something I have never seen before so I have no basis for thinking your conclusions are not correct. The use of sleeves along the cord end is quite a novel advance from the viewpoint of facilitating replacement of cords (which might be necessary more frequently than with North American equipment if the plugs tear off so easily!) but if the plugs did not tear off, the use of individual spade tips as done in NA would be adequate.
It sounds like your observations and conclusions about this are accurate.
Quote
Unfortunately, when I tried this, I discovered that only 3 cord pairs (call and answer) out of the 8 gave any resistance reading at all. They were however consistent. The "black" terminal gave no measurement (ie. the meter stayed at 1), nor did any of the yellow terminals. The red terminals on the call and answer cords (of the 3 pairs that registered anything) all gave a resistance reading.
That's puzzling. Perhaps there are broken leads on the lever keys.
OTOH, since the assignment of cord circuit lead connections to the cords is predetermined by the mechanical arrangement of the 3 ferrules or sleeves (what you called "rings") on the switchboard end of the cords and by the progressively longer leads at the plug end, it's really a non-issue: proper reconnection is almost inevitable. However you will have to figure out why the circuits are open towards the cord circuits to get the swbd working.
Just to reconfirm: when you made these continuity measurements towards the cord circuits, were the (+) and (-) power supply input leads short circuited and the battery cutoff switch (if any) turned on?
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re. the hand-piece:
The hand-piece cord has three wires, red black and white. Black is the wire common to the mic (receiver? - sorry I'm new to telephones) and speaker.
The "mic" or speaking end, is the transmitter. The "speaker" or listening end, is the receiver. It's possible the BK is the lead which is common to both. I have no way to know. You still need to determine which is the TRANS and which the REC lead.
QuoteUsing a 19V DC supply, unfortunately I could measure nothing across the terminals in #25
Later, I'll attempt to trace how far the 19V gets in the switchboard.
All the best
It's quite possible that DC is not applied to the transmitter unless a cord circuit TALK key is operated. If there is a battery cutoff key (perhaps RB or more likely NB) it would have to be ON too.
All the best to you too.
A quick reply to this abandoned thread and to Alex G. Bell and unbeldi in particular: sorry I disappeared last year. I had to have a surgery and some medical treatment and this project fell by the wayside. All's well now and I'll be back working on this again starting next week. If you're still around to answer my questions, that would be great! All the best!
Unfortunately, Both Elvis, and Alex have left the building.
They ARE missed.
But, there are a lot of brainiacs here eager to help. :)
Good luck on your board.
That's great, thanks!