Phone call affects internet access - does this make any sense?!

[silverblade]

Just had an incoming phone call on our landline.

As soon as the phone was picked up the internet basically ground to a halt. I was getting ping responses up in the 40,000 ms range to google.com 

I opted to reboot the modem whilst the phone was still in use, which then reconnected straight away and everything went back to normal. Except...

I've been keeping an eye on the sync speeds. It was previously connecting at around 10mbps. Now:
DSL Speed:  855/12151kbps

Did the incoming call cause lots of noise on the line and cause a shift to a different frequency range? (or however ADSL2+ copes with line noise.)

I do have filters installed etc. so it surprised me even that a phone call could cause this.

Am I missing something? 

[Rik]

Faulty filter would be the most obvious cause, SB. Check that by substitution, if that fails to eliminate the problem, it might be a rare fault known as an HR circuit.

[silverblade]

Sure, I've got a few spare filters so I'll try swapping it over. Is there any difference between ADSL and ADSL2+ in terms of filterage? I'm guessing there won't be a difference.

("HR circuit" paints a strange mental image...)

[Rik]

No, the filters are the same, but not all filters are created equal, so you might want to try and ADSL Nation xf-1e if those at hand don't solve it. Also try a different phone, just in case.

HR = high resistance, where the circuit can have a joint that can act as a diode, effectively.