I have broadband via a BT line, and 4 dial-up accounts.
Plug your filter into the phone socket, with the modem, (or router), connected to the appropriate socket. In the other socket of the filter I have a double adaptor. Into this is plugged the telephone, and the lead from the 56k modem in the PC. Works fine!.
I cannot comment about using cable broadband as I have no experience of this.
My method is very similar to anchor but I have a dedicated broadband cable to the BB modem and, from the phone side, a double adapter carries the extension lead for the PCI modem plus another extension lead (with a second double adapter) for the main cordless phone and an answering machine.
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