Actully, a DSL filter is a low pass filter, to keep you from hearing the higher frequency DSL signal over your conversation.

Here is a link to a schematic:

https://www.benjammin.net/www/pages/techtips/dsl-filter.html

I have several old phones, an Automatic Electric 40 desk set and also a wall set, the frequency response of those doesn't pass the DSL into the earpiece, so no filter necessary on them.



[This message has been edited by Touch Tone Tommy (edited June 10, 2004).]