Cable signal detector

The utility model provides a cable signal detector can pull out through the mistake that the demonstration has or not information and communication to restrain communication cable, can use the communication cable who generally uses. Cable signal detector sets up in connector (3) that the tip at communication cable (2) set up, perhaps sets up in relaying connector (4) of connecting this connector (3), cable signal detector has: rectifier circuit (12), its partly branch that makes the signal of communication cable (2) transmission takes out partial signal to the rectification is exported for the direct current, comparator (13), when its output voltage at rectifier circuit (12) is more than preset's the threshold voltage, output predetermined voltage signal, and luminous circuit (14), it is luminous when comparator (13) output predetermined voltage signal.