iDect SOLO 5035+2 Owner's Manual page 12

If you have a broadband line
If you connect your telephone to a line with a broadband connection, you
will need to insert a micro-filter between the telephone and the
telephone line; otherwise you may get interference between the
telephone and the broadband, which could cause problems.
In a home with broadband, every telephone must have a micro-filter
connected, not just the one at the telephone point that your modem is
connected to.
If you need more broadband micro-filters contact your broadband
supplier.
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