Sigalarm has been at the forefront of safety innovations for decades. We are proud to share a recently discovered artifact that highlights a field evaluation from 1973.

Consider where YOU were in 1973. Did you have a cell phone? Did you have a personal computer or laptop? How about your car? Did it open or start without inserting a key? I could go on and on, but you get the point. Drastic lifestyle improvements have been advanced over the decades.

Thankfully, technology has also evolved that protects and saves lives!

Historical Field Evaluation

Here is the opening of that thorough field test from 1973,

ABSTRACT: This report examines the use of a proximity warning device on a crane boom to provide a warning when the boom approaches a predetermined safe distance from an energized power line.

by Richard L. Reynolds, October 25, 1973

Two goals were established:

  1. If the device would operate properly in the mining environment for an extended period of time.
  2. If it needed any design changes to produce the margins of safety necessary to prevent future electrocutions resulting from contact of equipment with high voltage lines. As a result two recommendations were made by Mr. Reynolds of the United States Department of the Interior, Pittsburgh Technical Support Center. Both were implemented by Sigalarm.

Radial Swing Test

“It was found that while swinging the boom from either direction toward the reference point the device would product a warning when within 1 foot of the reference point”

Vertical Lifting Test

“In this test the alarm produced a warning within 1 foot of the reference point”

The following observations were made after a 6 month period:

  1. By placing the antenna 8 inches above the boom structure, there is no appreciable shielding of the antenna by the boom.
  2. The device gave consistent results during the test. It produced a warning within 1 foot of the set point regardless of the direction of boom movement as was demonstrated in the vertical and radial test.
  3. The device did hold up under vibration and varying weather conditions to which it was submitted.
  4. It was accepted favorable by the two crane operators at the time.
  5. The operator of a crane with an extendable boom should be aware that the device is less sensitive when the boom is not extended. This is a known factor even today and is addressed that when the boom is extended it naturally becomes more sensitive due to longer antenna.
  6. When the crane is operated between two power lines that are transmitting at different voltage levels it is possible that the device could be keying on the higher voltage line when the more immediate hazard is the lower voltage. Sigalarm responded by automatically setting our devices for maximum sensitivity. This means all sources of danger are detected at start up and when approached, set off the alarms. Also Sigalarm always recommends setting device to lower voltage lines on jobsite which would then automatically alarm further away from the higher voltages.


Because humans are human, mistakes can be made. Human error often results in tragedies and loss of life. But thanks to modern technology, some things can be automated to ensure safety. Our concern is about power lines. When a crane operator prepares his equipment for use, it is possible he could forget to activate the warning device. Sigalarm responded to this by automating our devices. As soon as the operator starts the crane, the proximity device is activated. ALL of Sigalarm’s devices have this as a built-in feature.



We have posted articles highlighting every aspect of danger in the work field. Often common sense guides us to make improvements.

Because there are constant improvements and advances in technology, Sigalarm is committed to keep up with every advance in order to keep workers safe.  This mandates that we keep ahead with all technological discoveries and modifications. We do this and apply it to every one of our devices.

If you would like to see the full field evaluation report or if you have any questions, just give us a call. We would be honored to help you keep your workers safe.