TM-507 ... Insulation Tester DISPLAY - 4 digits LCD display. - Polarity indication: Automatic polarity ¡¦ ¡V ¡¥ display for negative input. - Low battery indication. FUNCTIONS - Function keys: POWER, GO, ZERO,LOCK, BACKLIT. - Continuity test. - Measures high insulation resistance with auto range: 250V: 4M ~ 1000M Ohm 500V: 4M ~ 2000M Ohm 1000V: 4M ~ 4000M Ohm - Measures DC voltage (0V~600V), ACVoltage (0V~600V). - Auto power off. - Auto discharge