can I use a plain old 56k model built into my laptop with a adsl microfilter pluging into the telephone jack. The adsl runs to the adsl socket and I connect my modem to the phone socket. Can they run in parallel?
DSL works by multplexing the DSL signal and the voice signal on the same line, with the filters preventing the DSL signal from getting to phone equipment and preventing interference from the phone equipment within the DSL bandwidth. Since a 56k modem uses the voice bandwidth, both can coexist.