ADSL microfilter designed to minimise the effect of ADSL noise on your telephone or other telecom products. By separating the high frequency of ADSL & the low frequency analogue normal telephone equipment can be used without interference. This adaptor means that you can connect an ADSL modem & telephone to one telephone socket. Extension wiring can be plugged into the filter. If you have the wires only ADSL service you will need an ADSL splittermicrofilter on each of your phone sockets that can be used for ADSLmaximum of 4.