Author Topic: Brazilian Ericsson switchboard  (Read 1985 times)

Offline escuta

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Re: Brazilian Ericsson switchboard
« Reply #30 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.

Offline escuta

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Re: Brazilian Ericsson switchboard
« Reply #31 on: July 29, 2017, 04:27:50 PM »
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


Alex G. Bell

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Re: Brazilian Ericsson switchboard
« Reply #32 on: July 29, 2017, 04:42:29 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.
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.



unbeldi

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Re: Brazilian Ericsson switchboard
« Reply #33 on: July 29, 2017, 05:37:53 PM »
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.


 

Offline escuta

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Re: Brazilian Ericsson switchboard
« Reply #34 on: July 29, 2017, 05:41:47 PM »
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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.

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.

Alex G. Bell

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Re: Brazilian Ericsson switchboard
« Reply #35 on: July 29, 2017, 05:49:02 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.
« Last Edit: July 29, 2017, 05:53:57 PM by Alex G. Bell »

Offline escuta

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Re: Brazilian Ericsson switchboard
« Reply #36 on: July 30, 2017, 08:10:22 AM »
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.

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.

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Photo #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).

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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.

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.



Offline escuta

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Re: Brazilian Ericsson switchboard
« Reply #37 on: August 01, 2017, 09:45:21 AM »
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!

unbeldi

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Re: Brazilian Ericsson switchboard
« Reply #38 on: August 01, 2017, 10:51:29 AM »
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.
« Last Edit: August 01, 2017, 11:18:07 AM by unbeldi »

Alex G. Bell

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Re: Brazilian Ericsson switchboard
« Reply #39 on: August 01, 2017, 02:13:07 PM »
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.

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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.

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 180).

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.

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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!
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.
« Last Edit: August 01, 2017, 02:25:04 PM by Alex G. Bell »

Offline escuta

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Re: Brazilian Ericsson switchboard
« Reply #40 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:

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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.

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!

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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. 

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:

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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.

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.

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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.

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



Alex G. Bell

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Re: Brazilian Ericsson switchboard
« Reply #41 on: August 07, 2017, 02:55:17 PM »
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.
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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!
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.
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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.
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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
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.
« Last Edit: August 07, 2017, 03:07:11 PM by Alex G. Bell »

Offline escuta

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Re: Brazilian Ericsson switchboard
« Reply #42 on: April 20, 2018, 01:57:00 PM »
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!

Offline RB

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Re: Brazilian Ericsson switchboard
« Reply #43 on: April 20, 2018, 04:06:12 PM »
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.

Offline escuta

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Re: Brazilian Ericsson switchboard
« Reply #44 on: April 20, 2018, 04:34:10 PM »
That's great, thanks!