An effective way to eliminate the repeat calling of all those telemarketers. A bit unintuitive to set up, but once working it does the job. Make sure you use the included splitter to hook up your phone. Don't rely on the 'phone' port on the back of the unit. It didn't work for me. Also, it doesn't need batteries so ignore the battery compartment.
Block up to 1,200 incoming phone numbers & faxes in Blacklist (16 digit each)Block up to ten (10) incoming area codes and/or prefixes (up to 10 digits each)Block up to 100 outgoing phone numbers (with owner's passcode)Block calls with no caller ID information (shown as unknown, private, out of area, anonymous, etc)Line powered (does not require batteries *** please discard battery compartment). User adjustable 16-digit Caller ID display shows phone numbers (no name), date/time. Works with most telephone services (PSTN, VOIP).