WE 557A PBX

[SparksNArcs]

Hello everyone! I recently became a volunteer at a telephone museum, and helped another member find a new home for a switchboard he had been storing for some time.  No better way to learn about how telephone systems work than to rig some old phones up and play operator!

The unit in question is a 557A PBX (to the best of my knowledge and the prior owner's), and I spent lots of time on the threads here researching electrical connections and diagrams. This unit wound up with all 100 Secretarial lines installed, which made moving it a challenge. So far I've managed to connect my benchtop DC supply to the BATT and GND posts, and successfully connected two Station lines together; the lights on the board come on when handset is lifted, and the cord pairs light up appropriately when connections are made or taken down.

At the moment, I don't have a ringing supply, so there are some functions I can't test yet. 

However, there are a few questions I had regarding how these PBX switchboards were used originally.

1. How were Secretarial lines and Station lines used typically?
2. What triggered the Secretarial lines to light up on the board, a ringing signal?
3. What are the blank jacks without lamps on the right lower panel called/ used for?

Unfortunately I don't have any history behind where the board came from; California is what the prior owner mentioned. There are four numbered Trunk lines, and one just labeled "Welcome Wagon", which makes me really wish this thing had some documentation!

[G-Man]

There is a plethora of technical information over on the TCI, but here is some info regarding of its development history: 

• https://www.telephonecollectors.info/index.php/browse/document-repository/catalogs-manuals/western-electric-bell-system/publications-and-educational-documents-by-date/blr/11542-57jan-blr-p6-answering-service-switchboards/file

The images are not very detailed but I suspect that the red that is seen above the lamps are plastic dummy plugs used to visually indicate to the attendant that those particular jacks are not active. Probably the other jacks you are referring to were used for conferencing.

Interesting that the WECo No. 6 dial has an AECo number card. I suspect that this board was used in General Telephone Co. of California (GTE) territory so they installed the card. If there is a number printed on it, we can tell where is was used.

And yes, GTE often purchased and used equipment that was manufactured not only by Automatic Electric, but also by Western Electric and others.

And oh, Welcome Wagon may have been one of their clients.

[Contempra]

Hello everyone...

Welcome to this forum..SparksNArcs..the best forum specializing in vintage and old telephones..

[HarrySmith]

Welcome to the forum.
Check my other post to a new member, you may want to read my warning

http://www.classicrotaryphones.com/forum/index.php?topic=27181.msg262190#

[paul-f]

There is a plethora of technical information over on the TCI, but here is some info regarding of its development history: 

• https://www.telephonecollectors.info/index.php/browse/document-repository/catalogs-manuals/western-electric-bell-system/publications-and-educational-documents-by-date/blr/11542-57jan-blr-p6-answering-service-switchboards/file

A long-term search link for the BLR article is...
https://www.telephonecollectors.info/index.php/search?q=blr+answering+service+switchboard

More...
https://www.telephonecollectors.info/index.php/search?q=557+pbx
https://www.telephonecollectors.info/index.php/search?q=secretarial

And a Google site search in the Library will lead to many other reference documents, such as CDs and SDs, etc.

[SparksNArcs]

...Interesting that the WECo No. 6 dial has an AECo number card...

The dial is actually just sitting on the desk, not hooked up at the moment. The unit previously had a touch-tone pad on the desk (associated circuitry hanging on the inside left of the cabinet), but the prior owner didn't like it and removed it in favor of the rotary; installation was not completed, however. Sadly I don't have the correct bracket to attach it to the desk, although all of the screws are present for that.

[SparksNArcs]

A long-term search link for the BLR article is...
https://www.telephonecollectors.info/index.php/search?q=blr+answering+service+switchboard

More...
https://www.telephonecollectors.info/index.php/search?q=557+pbx
https://www.telephonecollectors.info/index.php/search?q=secretarial

And a Google site search in the Library will lead to many other reference documents, such as CDs and SDs, etc.

Just looked at the first document regarding the 557A & B, which I had read before, but apparently not close enough! I'm a little young to remember when people didn't just have answering machines, so the concept of an answering service was a bit foreign. That did clear up a few things, though.

Based on that information, this is what I understand about the operation:
1. Central Office redirects calls on off hours from businesses to Answering Bureau, which lights up corresponding lamp on Secretarial panel.
2. Secretarial lines can be answered by the attendant for taking messages, or routed to a Station line to speak with a manager or other employee at the Bureau.
3. Station lines can call out on Trunk lines or to other Station lines, but calls cannot go out through Secretarial lines, and Secretarial lines cannot be connected to Trunk lines. 

My next question is, once the attendant had written down messages for various businesses, did they tie into a trunk line a dial out to each business to give them their messages the next day?

[HarrySmith]

I have a couple of switchboard dial mounts that I got in a box of parts. I would be happy to donate one as I have no use for them. I cannot tell from the pictures what it looks like.  Does anyone have a picture of the dial mount? If not I can post pictures of what I have in the next few days, after I dig them out, to see if they will work.

[G-Man]

My next question is, once the attendant had written down messages for various businesses, did they tie into a trunk line a dial out to each business to give them their messages the next day?

Typically the business would call-in to check for messages, i.e.- "Bessie, did anyone call while I was away" or "did anyone call while I was returning from the restaurant?"

Or if they were on duty, such as a doctor, veterinarian, plumber, or 24-hour diesel truck repair service, the answering service attendant would call the restaurant (or other location that they were previously informed of by the customer), where they were dinning at.

 They would also screen calls so the subscriber would not have to provide their private number and be bothered by annoying or frivolous calls at home, so the attendant would call only if it were urgent.

Also, the secretarial lines only respond to ringing current by means of a cold-cathode tube, so the attendant cannot simply plug into an idle line place outgoing calls or on a busy line to snoop on conversations.

[SparksNArcs]

I have a couple of switchboard dial mounts that I got in a box of parts. I would be happy to donate one as I have no use for them. I cannot tell from the pictures what it looks like.  Does anyone have a picture of the dial mount? If not I can post pictures of what I have in the next few days, after I dig them out, to see if they will work.

I would appreciate that! I'll get a better picture of the mounting location and the dial assembly later today. The desk has two threaded inserts one above the other, maybe 2" apart. The bracket is, I think, a U-shaped piece that the dial "clips" onto and secures with a screw or two.

[G-Man]

It would have originally been equipped with a rotary dial but had since been retrofitted with a DTMF dial.

I have included a jpeg showing the 25B-mounting bracket that would be needed to mount the 34D-adapter to the writing shelf.

[G-Man]

Also, where are you located? If you are close enough I probably have a ringing supply that I would be willing to donate. Otherwise, the cost of shipping would probably be prohibitive.

[SparksNArcs]

Also, where are you located? If you are close enough I probably have a ringing supply that I would be willing to donate. Otherwise, the cost of shipping would probably be prohibitive.

I am in Auburn, WA. I've started volunteering at the Connections Museum in Georgetown.

[SparksNArcs]

It would have originally been equipped with a rotary dial but had since been retrofitted with a DTMF dial.

I have included a jpeg showing the 25B-mounting bracket that would be needed to mount the 34D-adapter to the writing shelf.

That's what I was thinking of! The dial still has the fingers on the bottom to engage with the terminal board on the bracket, although they are a little bent.

[G-Man]

I am in Auburn, WA. I've started volunteering at the Connections Museum in Georgetown.

I suspect that Sarah and the crew at the Connections Museum would have extensive documentation and needed components including power supplies and dial brackets at their fingertips, etc., but perhaps not. Otherwise it would save you the cost of today's expensive shipping.