Testboy-20-Plus-Voltage-Proofed-Continuity-Tester-Testboy-TESTBOY-20-P-The-Testboy-20-Plus-is-a-Voltage-Proofed-Continuity-Tester-that-can-detect-AC-voltages-through-the-insulation-It-can-also-find-defective-lamps-in-chains-of-Christmas-lights-or-similar-accurately-within-seconds-P-P-The-electronics-can-also-perform-a-single-pole-phase-search-This-simple-to-use-&-the-versatile-tester-makes-the-Testboy-20-Plus-an-ideal-addition-to-the-toolkit-of-electricians-&-service-technicians