PRO Call Blocker by HQTelecom - Block Unwanted Calls - Latest Version Available Easy to Setup - Just plug-in one end to your phoneline and the other to your existing phoneline Easy to Use - Just press a button to permanently block unwanted calls Block up to 1,500 telephone numbers, and ten (10) area codes and/or prefixes (3-5 digits in length) Powered by the phoneline - It uses the power from your phone line, requires no batteries or power adapters. Compatible with FSK/DTMF, PSTN house landlines (tested with AT&T, Verizon, and many others), and VOIP services (Vonage, MagicJack, and others). Also Verizon FIOS, and cable companies (Comcast, CableOne, TimeWarner, and others).