The filter should be on the line for the voice phone, not the line to the 'puter's DSL card or to the DSL appliance to which the 'puter is connected. I had a similar problem here, though, right after my DSL was first installed. Voice wasn't even a consideration, as the DSL service was on a separate line which had been one line of a dedicated dial-up multi-line configuration, none of the phonelines/phone numbers ever used for voice service. Anyhow, I was experiencing frequent DSL connection failures. As part of the troubleshooting process, a properly filtered voiceline was split from the DSL wall jack and run to a phone. Sure enough, any time the phone would ring, the DSL connection would fail. Really irritating, as there was no earthly reason that phone should receive calls ... it has a non-published number, and that number was never given to anyone for any purpose. Once or twice, it turned out to be a legitimate wrong number, but every other call I physically answered, or that the Caller ID tracked, turned out to be telemarketers or the like. After a good bit of go-around with the telco, including disabling call reception for that particular phone line, it eventuated that a setting of theirs, on the DSL card in the distribution cabinet (sorta a remote central office) serving my neighborhood was incorrect. That eventually was remedied by them. On a humorous note, now, the DSL line does have a filtered voice split, which goes to the modem on one of my machines. Using that machine's fax software, I can send and receive faxes between that machine all the way across my desk to my actual standalone fax machine, which has its own phoneline. Who knows ... maybe someday that'll come in handy, I have no idea for what, but it was silly/fun to set up, and I can do it
BTW ... all my phone lines are are on the National Telemarketing Do Not Call list.