After installing ADSL recently I encountered several problems getting my USB Alcatel Modem to synchronise on the line. I tried everything, or so I thought...
After changing ADSL filters and phone cables from my USB modem to the phone socket I still was unable to get the little green LED on the front of the modem not to blink. According to the manual this synchronisation LED should switch from blinking to a solid green after booting the machine. However there was either a problem with my phone line or a problem between my master phone socket and BT's exchange.
I phoned my ISP and after confirming everything I had done he had run out of ideas for me to try. Before calling BT and fork out £60 on a call-out charge I thought I'd check the phone extension that extends the master socket upstairs. I unplugged the upstairs phone and tried synchronising.
I tried plugging in a different phone upstairs, but still the same problem. So it can't be the phone I thought. It must be the extension cable. Since ASDL runs at high frequencies a bad termination of the phone socket upstairs must be to blame for the problem, perhaps causing the signal to reflect and cause interference on the line.
So for now we can either have an upstairs phone or an ADSL connection. Oh well... one phone isn't so bad!