For ADSL Boardband users, if you often encounter problems like :-
1) ADSL disconnects whenever I pick up a telephone
2) My telephones have stopped ringing
3) My telephone line crackles & hisses when my ADSL modem is connected
4) Caller-display no longer works since ADSL was installed
5) The earpiece volume on my DECT phone is very quiet
there is a high chance that your microfilter is not working fine or you do not have enough microfilters as these are all classic symptoms of badly behaving microfilters or missing microfilters.
All active phonelines (attached to an active phone sharing the same phone line with the ADSL phone line) should be connected with a microfilter so that any incoming or outgoing calls will not disrupt your existing connection to the internet.
So for those ADSL Users who may be experiencing the above problems, please check that you have enough microfilters and all are working fine.
Some background to the need of a microfilter:
Because ADSL uses high frequency signals that are outside the range the human ear is capable of hearing, the service can operate over the same pair of copper wires as your ordinary phone line. However, to prevent the ADSL data signal from interfering with your regular telephones and other equipment such as fax machines and answerphones, a microfilter (also referred to as splitter) is required to "strip out" the data signal so that your analogue devices can receive the normal voice signal without interference.