To alert utility-line workers of overcurrent conditions on such aerialdevices as insulated ladders and truck booms, the Chance Sentinel soundsan alarm if leakage current reaches a pre-set level. The leakage settingadjusts from 1 to 1,000 microamperes in resolution increments of 0.1microamp. The audible warning eliminates the need to watch the actualcurrent level, continuously displayed on the Chance Sentinel#s digitalLCD screen. The alarm sounds immediately upon overcurrent and continuesuntil the condition is corrected. To also trigger a truck horn or otherexternal alarm, a jack on the instrument panel accepts a standard 1/4"two-conductor phone plug. A test terminal on the panel permits a simplecontinuity check of the monitor leads prior to each operation. Beforeeach use, the instrument automatically performs a rapid electronic selftest. Simple operating steps are printed on the inside lid panel. Adetailed instruction sheet also comes with each unit.