The EM1660 and EM1670 are Central Filters that require professional installation. Because they are installed at the gateway to a property, users can be ensured that all signals throughout a house are filtered and speeds will be maximised. As all houses are wired differently, wiring irregularities have impact on DSL speeds and disturbance on a line. By installing a central filter/splitter, you can eliminate any possible troubles that can be caused by irregular wiring. The EM1660 is a small sized indoor filter/splitter while the EM1670 comes in a weatherproof enclosure for outdoor installations. The EM1660 and EM1670 both conform to all local safety and Telstra standards.