The filter removes any noise/ interference from the line.
If you have Internet you will need a filter in every telephone wall socket in use in your house. We would prefer you plug a filter at the back of the cradle to ensure there is no noise or interference in your phone line. If there is noise in the line we would not able to transmit / collect the data from your scanner.
If you need a filter, we can mail out to you free of charge. Please contact us on 1800 456 997 option 2. Alternatively, you can email: email@example.com