Hi,

After a lot of searching over the web I'm more confused than ever regarding whether I can get Caller ID working on a PC on a BT landline. I know that almost any modem can provide this with the right software in the US, but there are various websites that suggest it is harder to find a modem that supports this in the UK. I simply want the PC to be able to display the caller ID on screen, and I'm not bothered about being able to use the PC to actually answer the call).

I'm not looking for a dial-up web connection, (I'm already on a wireless network and adsl router). For the record I'm using winXP, and would rather use a USB modem, instead of PCI.

(just to add to the confusion a PC World usb modem (Zoom 3090) is listed as supporting Caller ID type 2, but when I checked the support forums at the www.zoom.com website it said that it could only support caller ID when connected to the web via the modem)

Anyone know whether this is possible and how. If anyone has actually achieved it then even better.

Cheers.

In case your not aware this is how caller ID functions on a public exchange line.

Just prior to the public switch applying ringing current to announce an incoming call a short burst of data is transmitted onto the line. This data telegram is 1200 baud Async and contains information about the 'A' party, the originator of the call.

What you have to do is find a modem that will replicate this. That is sit across the BT line, without looping it of course otherwise your permanently engaged!, listening for this burst of data then upon receipt of display on a PC and also ignore the ring current that follows so as not to "trip the ring".

BT use ETSI FSK With PR.

Caller ID type 2 means that you can receive the Caller ID whilst already on a phone call, commonly know as Call Waiting ID.

BT supports call waiting ID, Telewest do not.

The site has details of CLID: http://www.ainslie.org.uk/callerid/cli_faq.htm

With a list of modems that allow Caller ID here: http://www.ainslie.org.uk/callerid/cli_faq.htm#Q_18

I'm not sure that the data is always sent before the phone starts ringing - on my ntl line, the Caller ID normally appears after the first ring (during the first ring it just says 'Call').

Dan

With BT it is sent before the first ring. With NTL and Telewest they use various other standards, differing on your location, therefore the data is not sent until after the phone starts ringing, except for areas that use the BT standard.

System 'X' was designed to send the data prior to sending the ringing current. When ringing current is being sent the line card in the public exchange has switched the ringing current and the associated off hook detectors onto the cable pair. Remember

There appears to be no reason why, the data could not be sent after the first burst of ringing current. However if this were the case and you were to answer the line on the 'first ring' the data with 'A' party information could well be lost.

Perhaps your caller ID decoder receives the data and then waits until after it has detected the first burst of ringing current before display so as to ensure it doesn't display a false message. i.e. data received without ringcurrent.

Depends on the francise area.

http://www.ainslie.org.uk/callerid/cli_faq.htm#Q_6

The Cable Communications Association in the UK developed their own standard which sends the data after a short first ring, as either Bell 202 or V23 tones. They developed a new standard rather than change some street 'boxes' (multiplexors) which couldn't cope with the BT standard, and Oftel let them get away with it. The UK cable industry use a variety of switches - most are Nortel DMS-100's, some are System X, System Y and Nokia DX220's, and some of these use the BT standard instead of the CCA one! The data format is similar to BT's, but the transport layer is more like Bellcore, so North American or European kit is more likely to detect it.

I guess it would be the line reversal part that the multiplexers couldn't cope with.

With respect to service from BT there is no guarantee of a line reversal upon CSA on a 'loop exchange line' being returned to the 'A' party so I can't believe that cable operators would behave any differently.

The only analogue exchange line that BT will guarantee reveral upon CSA is one configured for earth calling / ground start - which isn't normally requested by a domestic customer!

The only other application I can think of when a reveral is used, is the signalling of a 'B' party answer when DDI is deployed to a P.A.B.X. and that, of course, would be via a different interface in the street multiplexer.