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Message 1 of 3

Old caller display CD1500

I have an old BT CD1500 unit which has inch high numbers and letters and includes a 70 number directory of names which displays instead of the number, a brilliant bit of kit, mine has been working for many years on an ordinary line, then later with BT Broadband.
I just had BT infinity fibre broadband installed, and the last call displayed was the Openreach Engineer to say he was on the way. The engineer did not check to see it was working before he left as he should have done.
When the CD stopped indicating new calls I rang to complain, but when we realised that the caller id on my cordless phone was still working Openreach told me the CD1500 was obsolete and there was nothing they could do. The CD1500 still showed the time correctly and indicated when the line was busy as normal, just no incoming calls indicated. Very suspicious that the equipment was working perfectly until the engineers came! After some research I uncovered the following vitally useful information.
Early BT caller display equipment usually will NOT work on Cable phone lines as they use a different signalling standard, later equipment is mostly dual standard, but you do need to check before switching providers. Mind you most sales people BT or cable company have no idea of this.
The thing that brought my CD1500 back to life was when I discovered that the unit is polarity conscious. For most modern phone equipment it does not matter which way round the incoming pairs of the phone line are connected although this used not to be true, old BT pay hones and the now obsolete party lines were dependant on the line pair being connected the right way round, but not any longer.As a result most Openreach engineers are lax about ensuring that lines are connected with correct polarity, and this does not usually matter, but it does matter with early caller display equipment like the CD1500.

This was easily fixed and hey presto incoming calls are now displayed as before.

Of course only Openreach engineers are allowed to mess with the line in this way, so unless you are absolutely sure you know what to do then don't, because you won't want to pay Openreach' wickedly exorbitant call out fees to fix any problems you may encounter. They should however agree to send someone out free of charge to swap the wires as they caused the problem in the first case, but you do need to be sure this is the cause of the problem first. It is scandalous that you may be expected to agree to pay to find out if the problem is something as simple and preventable as this.
So if you have elderly BT caller display gear that suddenly stops working especially after engineering attention to your line then the polarity may be the reason.
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Message 2 of 3

Re: Old caller display CD1500

Hi I have the same situation as you


I have ordered BT infinity and waiting for my line to be activated, now my CD 1500 caller display is not working, but my other phones are


How to I get BT to change the polarity of the line as you describe ?


My Infinity is self installed, with no engineer visit





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Distinguished Sage
Distinguished Sage
Message 3 of 3

Re: Old caller display CD1500

The CD 1500 is not compatible with broadband, due to the fact that the filters in the equipment, cannot pass the correct signalling conditions. This has been known about since broadband was first implemented. I had a CD 1500, which stopped working when I got broadband, a long time ago.


If you need a stand-alone caller display, then all of the new models will cope with the DTMF data burst which is transmitted along the line, before the first burst of ringing current.


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