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Old 7th May 2016, 4:12 pm   #1
camtechman
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Default Identity Of This 'Vintage' Telephone/Intercom

I recently acquired this telephone/intercom(?) outfit.

The two black boxes contain only a solenoid bell and the round silver button activates the other's bell.

They come in a well worn box but without any printing on it, nor any trace there ever was (reminds me of something that was sold in Saturday newspaper "small ads" along with army surplus Trench Coats & Cut Your Own Hair devices or from the famous Headquarters & General store !! (LOL)

One box is embossed "A" and the other "B". They appear to be bakelite and possibly British made & not that 'vintage' as I suspect they are perhaps a 50-60's repros ? The hand sets have a carbon transmitter & mag induced receiver. The wiring diagram shows a battery symbol (possibly 3v ?)

The circuit/wiring diagram is embossed on the underside of boxes A & B.

At first only one bell (Box B) was working (when the button on Box A ) was pressed but the bell in Box A did not ring when the button on Box B was pressed.

However, I soon discovered that Box A would ring only if its hand set was touching/hooked on to the hook. This is not a fault as it is differently wired (so that an extra wire (looks original) makes contact with the hook (not so on Box B).

However the hand sets & hence the transmitter just about work but only after giving the carbon granules a ruddy good shake.

If it helps I can take more pics of the internals & wiring diagram.

Cheers
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Old 7th May 2016, 7:59 pm   #2
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Default Re: Identity Of This 'Vintage' Telephone/Intercom

It probably won't help to identify them, but a sight of the internals/diagrams would be interesting (at least to me, anyway). I assume they're functionally similar to the little wooden intercom 'phones, of which "Sterling" is an example, in which ring button connects battery across line to ring DC bell in other unit (if on-hook).
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Old 7th May 2016, 10:10 pm   #3
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Default Re: Identity Of This 'Vintage' Telephone/Intercom

Thanks for the reply Dave, I'll post some more photos on here tomorrow.
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Old 8th May 2016, 10:26 am   #4
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Default Re: Identity Of This 'Vintage' Telephone/Intercom

A really nice set, looks like Dave and I almost always have the same interests, and solutions. I am sure we may make a diagram based on a good series of photos.

Do you plan to put it up for use/demonstration?

dsk
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Old 8th May 2016, 6:50 pm   #5
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Default Re: Identity Of This 'Vintage' Telephone/Intercom

OK, here's some pics (they'll be posted on this & the next page):

Firstly, as the units are near black bakelite some pics are only fair.

To help, I scanned the under side of the bases: A & B where there is connection diagrams (they are the same) but to enable details I've added white print to aid viewing.

You'll also see, on the scanned pics, I've coloured the knurled wire clamping nuts to show they are positioned differently A versus B bases.

On Base A, I've taken a pic with the bell dome removed to show the copper wire that's connect to the support post, this is not present on Base B.

I have noted that there is some difference to the way the handset wiring is wired to Base A versus Base B but I can't get a clear photo and will post a hand drawn sketch later.

Hope these pics help?

P.S. There is a maker's logo & number on the under side of the bases.
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Old 8th May 2016, 6:52 pm   #6
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Default Re: Identity Of This 'Vintage' Telephone/Intercom

More pics:
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Last edited by camtechman; 8th May 2016 at 7:02 pm.
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Old 8th May 2016, 9:26 pm   #7
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Default Re: Identity Of This 'Vintage' Telephone/Intercom

I'm assuming from the handset having only two wires, that the transmitter (T) and receiver (R) are wired in series, so that in the off-hook state the two handsets are connected in series across the battery. Presumably, the receivers are of a design that doesn't mind having a DC current passing through them.

I'm having rather more difficulty working out how the signalling works. The call button shorts out the handset and connects it to the call switch of the other unit via terminals "1". The trembler of the bell appears to be connected only to the hook, so I assume that a circuit is made between the hook and some part of the handset to enable the bell in unit A while on-hook.

If unit B doesn't have the wire from the trembler to the hook, is there by any chance a wire between the trembler and terminal "1" (the call switch)? It must be connected to something for the bell to work.
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Old 9th May 2016, 10:17 am   #8
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Default Re: Identity Of This 'Vintage' Telephone/Intercom

Is it a hook switch or press to talk button anywhere so the battery not will be in use when both handsets are on hook?
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Old 9th May 2016, 11:27 am   #9
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Default Re: Identity Of This 'Vintage' Telephone/Intercom

My earlier response was based upon the assumption that the handset is connected between "B" and "2" on each unit, but on closer inspection of the pictures of the two bases, I notice that on unit B, the handset terminals are labelled "B" and "1", which rather alters matters. I'll go away and have a rethink. I now have to head off to a meeting, but I'll look at it again this evening.
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Old 9th May 2016, 12:11 pm   #10
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Default Re: Identity Of This 'Vintage' Telephone/Intercom

To assist further, when I get a moment, I'm going to figure out both A & B's circuitry/wiring and come up with a schematic diagram/s and that way I'll get an understanding too.

Just to add, another feature of this unit is that both hand sets have a momentary push rocker switch in the handle and what they do, I have no idea and how it's connected/wired will require them to be dismantled but I'll have a go at taking them apart and let you know.

Watch this space.
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Old 9th May 2016, 12:29 pm   #11
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Default Re: Identity Of This 'Vintage' Telephone/Intercom

Pretty much guessing here, but it could have been like this.
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Old 9th May 2016, 12:53 pm   #12
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Default Re: Identity Of This 'Vintage' Telephone/Intercom

dags,

Thanks for that diagram, it'll help when I draw up mine.

Watch this space
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Old 9th May 2016, 7:25 pm   #13
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Default Re: Identity Of This 'Vintage' Telephone/Intercom

i dont know what they are but I would like a pair

They look great!
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Old 9th May 2016, 9:45 pm   #14
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Default Re: Identity Of This 'Vintage' Telephone/Intercom

May this thread be about a similar set (circuitry)??

http://www.classicrotaryphones.com/f...3481#msg123481
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Old 10th May 2016, 8:19 pm   #15
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Default Re: Identity Of This 'Vintage' Telephone/Intercom

Dags' circuit certainly looks sensible and should work. The problem I have, however, is that the information available from the pictures doesn't seem indicate that they are wired this way - especially in that the connection diagram on the base of unit A shows "1" on this unit connected to "1" on unit B, likewise, "2" connected to "2", whereas (as shown in Dags' circuit) it seems more logical to connect "1" to "2" and vice versa.

Is there any chance that Camtechman could post a picture of the internals of unit B? Also, confrimation would be helpful that (as shown by Dags) the suspension loop on the handset of unit A is connected to "2". With this information, it may be possible to establish a definitive answer regarding the wiring.

By the way, are they wired "1" to "1" and "2" to "2" to get them working (as shown on the base) or "1" to "2" and "2" to "1" (the logical way)?
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Old 11th May 2016, 1:32 pm   #16
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Default Re: Identity Of This 'Vintage' Telephone/Intercom

Firstly, although an electronic engineer of many years, my experience with telephones & intercoms, especially vintage items is not second nature to me.

However, my knowledge of laser guided missiles for the Typhoon Eurofighter was first class, albeit rapidly fading since my retirement from BAE Systems, Basildon some 10 years ago and so, to get an instinctive grasp of how these units are designed to work, I'm in the process of completely dismantling both units down to their individual component parts.

It's frustrating, that such a 'simple' device like these, has got me baffled but soon I'll be able to grasp it.

Whilst deconstructing the units, it's now obvious that the A & B units have their own individual differences & peculiarities but both have some moisture corrosion to screws & washers that make contact to some internal wiring terminal posts, which I will remedy & replace before re-assembling and testing.

Earlier I mentioned that each hand grip has a momentary push switch and I've discovered that this connects individual & separate metal tubes that are individually moulded to the receiver unit & the transmitter units but these are differently wired in set A to that in Set B.

By the time I've sketched, repaired & re-assembled these items & drawn up a schematic I should be able to understand how they work.

Watch this space.
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Old 11th May 2016, 6:36 pm   #17
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Default Re: Identity Of This 'Vintage' Telephone/Intercom

It is often that the simple things that confuse me to, once sorted and understood I admire them. Once you get a few switches the number of states a bit of stuff can be in is many more than the total component count, the brain goes a bit vague then.
 
Old 18th May 2016, 7:39 am   #18
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Default Re: Identity Of This 'Vintage' Telephone/Intercom

Quote:
Originally Posted by camtechman View Post
Watch this space.
Did you ever get any further with this?
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Old 18th May 2016, 8:43 pm   #19
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Default Re: Identity Of This 'Vintage' Telephone/Intercom

This is still alive thread and I'll be back soon.
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Old 12th Jun 2016, 9:38 pm   #20
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Default Re: Identity Of This 'Vintage' Telephone/Intercom

To keep this thread active.

I'm due to have an operation on 18th June and in the meantime I have restricted movement and so, I've not been able to provide anymore info but once I recover from surgery, I'll be keen to take advice from you all.

Bye for now, the nurse (my Sister) is nagging me to go to bed.
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