Principles of Operation SIGALARM's Power Line Proximity Warning System performs in two different modes: 1.As an automatic early warning system. Anytime the system is turned on, whether activated at engine start up (wired through the ignition) or by the power switch on the front of the control panel, it will automatically be set at its most sensitive setting. At this setting, the system can sense as little as 110 volts AC, warning the operator (and crew) that he is in the vicinity of a high-voltage power line. The operator need not set or adjust the system for it to operate in this early warning mode --- it occurs automatically! 2.As a proximity warning system. Once the operator has been alerted to the presence of an energized power line in the vicinity of his work area, he may choose to stay far away. If the job assignment calls for working in close proximity to the power line --- please, no closer than 25 feet --- the system can be set to alarm any time the boom comes within the preset distance. The entire length of the SIGALARM sensor antenna continuously receives (detects) the signal (electrostatic field) produced by all energized power lines. This signal is amplified by the electronics on the main control unit. "Course" and "Fine" controls allow the operator to set the alarm circuits to "go off" at a predetermined distance from the power lines, producing both visual and audio warnings. The repetition rate of both the visual and audible alarms increases as the boom or extension moves closer to the "hot" power line. SIGALARM continues to warn until the boom is withdrawn from the danger zone. For more information on how SIGALARM can help your company,