USB ISDN TA and telephone connection problem

[areid 0]

I have a domestic telephone installation with 2 analog and one digital ISDN line (provided by British Telecom under the name 'Home Highway'). The ISDN line is connected via a CAT5 patch cable to an external USB Hayes Terminal Adapter, and from there to a laptop via a USB cable. The arrangement worked fine for a few months, but now when the TA is plugged into the laptop (not necessarily connected to the internet), neither audio line can dial-out, and incoming calls are distorted. On its own the ISDN connection works fine. As far as I know I have not done anything recently to change the setup.

 

if I connect the ISDN line to another (desktop) pc via an internal TA card (Hayes Accura), and there are no problems whatsoever, so I guess it is something to do with using an external adapter, the USB ports and/or my laptop.

 

I have contacted Hayes tech. support and apart from recommending the latest drivers (which I have installed), they cannot suggest anything. British Telecomm are not much help either - as the line works ok with the internal PCI card they are convinced it is a laptop/driver problem.

 

I know many of you folks will not be familiar with UK telephone systems, but hopefully someone out there may have experienced a similar problem and/or have some idea how to solve the problem.

 

 

Other info. that may be relevant...

Operating system - XP Pro (SP2)

USB Host Controller Type - VIA Rev.5 or later

The is the only USB device connected to the pc.

Whether I plug the TA directly into the USB port, or via an externally-powered hub makes no difference.

I have applied the recommended USB 1.1 filter patch - no change.

I have updated my BIOS to the latest version.

The USB controller is sharing the same IRQ (10) as the on-board 56k modem (which is not connected to any line). I've tried to change the USB IRQ, but this cannot be done on my laptop.

In the device manager, the TA has installed itself as a 'NDIS WAN miniport adapter', which claims to be working correctly.

 

Any help would be appreciated. Currently I am having to connect to the internet via. 'snail pace' audio line 2, which only runs at 56k (well, about 45k in reality).

 

Alan