Test Lights are designed for low-cost monitoring of water conductivity. Operation is simple: the neon lamp is on when the conductivity is below the threshold value, the lamp turns off when the conductivity rises above. The fail safe design signals trouble if there is a power failure or the bulb burns out. For custom thread sizes or threshold values, consult the factory. The Test Lights incorporate an isolation power pack. The Power Pack isolates the test light and user from the power source. In addition to a reduced risk of possible shock, it will add to the life of the test lights where power lines are subject to voltage spikes. The Test Light is also available in a remote model. The neon lamp can be panel-mounted 15 feet (50 feet maximum) away from the testing cell.