Panasonic KX-TG6700AL Operating Instructions Manual page 12

Preparation
If you subscribe to an ADSL service
Please attach a noise filter (contact your ADSL provider) to the telephone line between the
base unit and the telephone line socket in the event of the following:
– Noise is heard during conversations.
– Caller ID features (page 30) do not function properly.
Example: ADSL line is line 2
12
To single-line telephone sockets
Noise filter
Line 2
Line 1