As of 2014, the vast majority of (UK) broadband accounts are DSL
broadband accounts (typically an ADSL account, but that's another
discussion). DSL is a technology that works upon the copper line
telephony network: it enables a copper telephone line to simultaneously
support an Internet connection and an analog telephone connection.
To connect to the Internet with a DSL broadband access account,
a user will require a DSL modem or router.
When DSL is activated on a phone line, it produces a high frequency
signal; higher than the human ear can hear. This high signal frequency
interferes with devices designed for voice communication. Therefore
a DSL filter must be placed between the analog (voice) devices to
block the high frequency signal from reaching them. Static line
noise will result from analog devices being attached without a filter.
Therefore, a DSL filter is required to avoid interference when
analog devices are attached to the DSL activated phone line.
The important fact to note is the filter is only required for analog
devices, such as:
- fax machine
Applying a DSL filter between the DSL modem and the phone jack
will result in the modem not establishing a connection. Therefore,
a DSL filter should be used between the phone jack and a telephone,
fax machine etc, but, it should not be used between the phone
jack and the DSL modem.
A DSL filter is different to a micro-filter: a DSL filter
has one input, designed for analog devices; whereas a micro-filter
has two inputs, one for the analog device and one for the DSL modem.
DSL filters are often confused with micro-filters, and in Australia
and North America, micro-filters are often referred to as line splitters.
If the DSL modem does not share a phone jack with a telephone
- Plug the phone cable directly from the modem into the unfiltered
(while a micro-filter can be attached, it is not neccessary, as
the DSL input in the micro-filter is wired straight through without
If the DSL modem does share a phone jack with a telephone
- Use a micro-filter, which has an input for the modem and the