What factors determine if Caller Display actually works?

[#1]

I have just changed my number due to some regular nuisance calls (although after two days I have already recevied another one, so that was probably a waste of money).

Anyway, I have also been paying for Caller Display pretty much since joining Plusnet 2 years ago, but it's success is extremely random and poor.
Most of the time I get no number showing up on my phone so I end up having to answer it anyway.
And yet when I press 1471 after the call, it is able to tell me the number, so why did the Caller Display function not work?
Why should I get an unsolicited call on a 'new' number that's supposedly been inactive at least 6 months?
And why does my Caller Display not work as it is supposed to?
I reckon I must be wasting my money paying for it every month, but I'd be interested to know if anyone has any answers to this before I just give up and accept the calls, or do away with the line altogether.

[#2]

Could be a fault with your phone (or caller display unit if separate).
Could be an inadequate CLID signal from the exchange.
What does your display show when the phone rings and caller display doesn't work?
Is it just blank or does it say something like 'unknown'?

[#3]

it just says the word 'calling' . lol - very useful.

[#4]

Interesting this as occasionally when I get a call from my Daughter it doesn't display her name, just 'incoming call'.
Usually her name is displayed.
Plusnet is my phone supplier.

[#5]

I wouldn't mind it once in a whille, but it is very rare that it displays the number. I don't know what to do. I continue paying each month, hoping it will work, but it hardly ever does.
I've seen a call blocking device but I'm not sure if it will work on my system - 1471 works ok, but will such a device function if caller display has something wrong with it ?

[#6]

It could be an ADSL filter that's blocking the ID signal or have you already tried that theory out?

[#7]

No I havent RP, I must admit I only have basic knowledge when ti comes to placing of these filters
If it's relevant, I also have a poor internet connection, which (without going into the details here) some good people over on the broadband forum are currently helping me with.
I only have two filters: one at the sky box, and one for the router. - this one also has the phone plugged into it, which I hope is correct, or should I have it plugged soemwhere without a filter?

[#8]

Well, if during your broadband troubleshooting when modem is off and not connected, you may want to try out if CLID is working at all on your line. Plug in the phone with CLI into the master socket on its own (without filter) and try a ring back test with BT line test (17070 option 1). Hang up and you should get a call from an 0800 number, if that doesn't show up in this setup then it's likely to be the exchange or the CLI device (but more likely exchange if it does show up on rare odd occasions).
Edit: Forgot to mention, your current setup seems correct, with a filter before any phone device.

[#9]

Thank you, I'll give it a try as you advise when I'm able.

[#10]

Quote from: Strat

Interesting this as occasionally when I get a call from my Daughter it doesn't display her name, just 'incoming call'. Usually her name is displayed. Plusnet is my phone supplier.

A bit late coming to the thread, but I would suggest the phone is not registering the data sent at the start of the ringing. I had no phones connected while checking my broadband; plugged in one and, just before plugging in the second, the first phone started to ring. On plugging in the second phone "incoming call" appeared - the only time I have seen that. The other phone registered the number.
Phil

[#11]

Thanks Phil,
after various tests (as I have also been checking my wiring to speed up my broadband), I have eventually tried a new phone and it works fine, so it does seem to have been a problem with the phone

[#12]

There are several different ways that a nusance caller picks you to call.
Obviously a lot come from some sort of database or prior contact, but others come from
computer controlled 'random' dialling.
So you have a group of people on the call centre.
The computer dials the first number on the exchange, if its engaged, or a fax or a computer it hangs up
if its answered it puts the call through to an available operator.
it then goes on to the next on the exchange
So your number need not be known at all for you to be called.
In a similar way many large companies or marketing agencies use computers to dial from contact lists
for marketing or legitimate reasons, eg debt collection or even returning calls.
You  can always tell a computer originated call because of the delay before the operator comes on.
This also explains 'silent' calls, this happens when the passover to the operator fails after the call is answered.