Digital Phone Line Tester - Multi-use RJ11 Digital Phone Line Tester.Digital Phone Line Tester features include: Built-in LED indicator allows testing of RJ11 4and 6 position phone outlets for common trouble conditions such as dead or open lines, reversed polarity, and AC voltage Detects dangerous surge in digital or analog phone lines lines Surge suppression circuit protects against voltage spikes and surges Tests 2-Line phone systems Tests for Polarity Uses standard RJ11 jack and plug Order Qty of 1 = 1 Piece Below is more info on our Digital Phone Line Tester