Morris Products 59180 Digital Phone Line Tester Plastic Imported Digital Phone Line Tester - Multi-use RJ11 Digital Phone Line Tester. Built-in LED indicator allows testing of RJ11 4&6 position phone outlets for common trouble conditions such as dead or open lines, reversed polarity, & AC voltage Detects dangerous surge in digital or analog phone lines lines Surge suppression circuit protects against voltage spikes & surges Tests 2-Line phone systems