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Old 2nd Oct 2017, 6:14 pm   #1
jmggurr
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Default Ericsson 1071 wiring advice

Hi all,

First post here, and first time vintage telephone owner - hello everyone!

I bought a British Ericsson 1071 wall phone (c.1948?) from ebay hoping I can get it working again on my UK setup and I am hoping for some guidance.

I want to locate it in my hallway close to a working GPO bell and ideally connect it via that bell.

The bell has a four-wire cable running into it with orange and blue connected to the bell (orange to T1 and blue to T4, green and brown unused). I was wondering if there is any way I can connect my new Ericsson phone to this wiring somehow.

Any help you can offer would be very gratefully received!

Best regards,
Jake
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Old 2nd Oct 2017, 8:16 pm   #2
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Default Re: Ericsson 1071 wiring advice

Hello Jake and welcome to the forum.

The N1071 has the same innards as the 332 instrument and is connected the same way. If your instrument works without a 3k3 resistor in series with the bell, just leave it with a solid link between terminals 11 and 12. A 3k3 resistor may be needed (as shown) if your telephone doesn't ring properly or draws sufficient ringing current that other instruments on your line don't ring properly.

I have an N1071 in the hall, and have had it years without problem. Mine was on an internal PAX system installed in about 1954 and I salvaged it in '84.

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Old 2nd Oct 2017, 8:23 pm   #3
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Default Re: Ericsson 1071 wiring advice

I'm assuming, perhaps wrongly, that your telephone is installed using a master LJU rather than be hard-wired. Could you tell us how your system is wired and how your extension bell currently fits into the scheme of things? Do the orange and blue wires to your extension bell in the hall connect to terminals 3 and 5 in the master LJU for example?
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Old 2nd Oct 2017, 8:29 pm   #4
jmggurr
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Default Re: Ericsson 1071 wiring advice

Hello Russell and thanks for your message. This probably sounds dense, but is there an obvious way I can establish which colours of my existing cable (orange, blue, green, brown) I need to connect to which terminals within the phone?

Sorry - completely new to this!

Best regards,
Jake.
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Old 2nd Oct 2017, 8:53 pm   #5
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Default Re: Ericsson 1071 wiring advice

It's a reasonable question.

Before we proceed, can you tell me if your telephone wiring is of the 'plug-in' variety, or whether it's hard wired? How is your existing telephone connected to the system? Does it plug into a socket or does it go to a junction box with a single screw in the centre of the cover?
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Old 2nd Oct 2017, 9:04 pm   #6
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Default Re: Ericsson 1071 wiring advice

Hi Russell,
Firstly apologies for appearing to ignore your second message but I didn't see it!

My box was installed within the last three years by BT but is buried behind a book case. I shall empty and move that tomorrow and investigate and come back to you.

Thanks for your patience!!

Best regards,
Jake.
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Old 2nd Oct 2017, 10:01 pm   #7
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Default Re: Ericsson 1071 wiring advice

Jake,

Have you any extension telephone sockets?

I suspect that the two wires leading to terminals T1 and T4 of your bell are connected to terminals 3 and 5 of either your 'master' socket or any one of your slave (extension) sockets - if you have any.

Without getting too previous, and to keep your system 'universal' (ie: suitable for use with other converted telephones you might acquire), if you adjust the wiring links in your N1071 as per my diagram in post #1 (apart from fitting a standard BT plug and lead, which may not be necessary) you will be in a position to connect it - and the bell - to the system. And if you wish to keep the extension bell 'paired' with your N1071, it would be possible to connect the bell directly to the N1071 via 'hard wiring' in lieu of the 3k3 resistor.

Before going further and to save confusion, it would be a good idea if you could trace the wire at your bell back to where it connects to your system and tell us to where the coloured cores are connected, and whether the green and brown unused cores are present and able to be used.

Have you a multimeter?
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Last edited by russell_w_b; 2nd Oct 2017 at 10:07 pm.
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Old 2nd Oct 2017, 11:02 pm   #8
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Default Re: Ericsson 1071 wiring advice

Here are two options using your existing wiring, provided the wire to your bell leads back to a master or slave socket and you can terminate all cores. The colours aren't important but the numbers of the terminals are.

Option 1 is the 'modern' plug-and-socket way using the capacitor in the master LJU and wiring all bells beyond it in parallel. I haven't shown it, but you may need an additional 3k3 resistor in series with your extension bell.

Option 2 wires both bells in series through the master LJU capacitor. This arrangement will see a power-factor improvement as the two bells in series will be better tuned (electrically) to the LJU capacitor and the ringing current will be almost in phase with the voltage. But the ring will be superior! You may need one 3k3 resistor in series with both of the bells, but try without.
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Last edited by russell_w_b; 2nd Oct 2017 at 11:22 pm. Reason: clarity (I hope).
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Old 4th Oct 2017, 3:56 pm   #9
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Default Re: Ericsson 1071 wiring advice

Hello Russell,
Apologies for the wait - work getting in the way of the fun stuff.

Finally managed to empty and move the bookcase and as you predicted blue is connected to T5 and orange to T3 with brown and green not connected at present.

I should clarify my wiring. This consists of a single master box and just the four core cable to the bell as mentioned.

I can follow your wiring diagrams perfectly, thanks very much for those. I shall have a crack and let you know how I get on...

Thanks very much!

Best regards,
Jake.
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Old 4th Oct 2017, 8:56 pm   #10
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Default Re: Ericsson 1071 wiring advice

Hi Russell,
Thanks very much for the wiring diagram - very helpful! And success! I went with option 2 but without the resistor for the time being because I don't have one yet. The bell isn't ringing but I am hoping this is because of the absence of the resistor. Also the earpiece is very quiet so I will have to have a look at that but I just wanted to say a big thank you for your invaluable support.

I will be in touch with updates soon!

Best regards,
Jake
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Old 4th Oct 2017, 10:46 pm   #11
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Default Re: Ericsson 1071 wiring advice

Hello Jake,

Which bell isn't ringing? The one in the N1071 or the existing extension bell? If you chose Option 2 the easiest way to prove you're getting ringing current to the bells is to short one of them out and check the other one rings satisfactorily. I would've thought you'd get at least a 'ting'. I had a similar arrangement with a Bellset No:26 and a 706 wired together and to a BT plug and it worked a treat.

Are your connections to the terminals 2, 3 and 5 in the master box all satisfactory? It might be a good idea to check your N1071 out on a standard BT plug and lead first before hard-wiring it to address any issues before putting it onto the system.
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Old 7th Oct 2017, 8:11 am   #12
jmggurr
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Default Re: Ericsson 1071 wiring advice

Thanks Russell, unfortunately my BT box is buried behind a book case so I cannot plug in another lead to test it. I used a holesaw to the back panel of the book case and the phone bases station, wireless router, house alarm are all on a shelf of that book case. It's a right faff to get at and therefore easier to test it in situ rather than move all the books again! I am confident of the connections at the BT box though. I still don't have the 3k3 resisters yet nor a proper cable to extend the run from my GPO bell to the N1071 so once that arrives I shall have a tinker.

Best regards,
Jake
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Old 7th Oct 2017, 8:23 am   #13
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Default Re: Ericsson 1071 wiring advice

Did you connect your existing wire to terminals 2, 3 and 5 of your socket when you managed to get behind the bookcase, so bringing them out to a point in your existing bell where you can work with them?

You need to have all three connections readily available at either your existing bell or your N1071 (which I take you to be connecting without fitting a 'slave' LJU) before you can make progress.
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