Response is seen on LED plus an audible tone is heard. Features include: Standard cable lengths: 90 mtr. brass electrode is field replaceable. Reel-type spool for lowering cable and electrode assembly. Reel is mounted on a tubular stand. Self-contained 9V battery power supply -no danger of shock from an outside power supply. Battery test. Standard brass electrode. Reel handles are shaped to fit your hands. Accurate to +1% of reading. Each Water Level Indicator is supplied with a battery.