Article
We’ve used signals for communication for eons. One of the most famous 
signaling scenarios allegedly happened during the American colonies’ 
struggle for independence. Memorialized in the poem “Paul Revere’s 
Ride,” written by poet Henry Wadsworth Longfellow, the passage is quoted
 here:<br><br><i>“One if by land, and two if by sea;<br>And I on the opposite shore will be,<br>Ready to ride and spread the alarm<br>Through every Middlesex village and farm,<br>For the country-folk to be up and to arm.”</i>

Are You Sending the Right Signals?

Steve Maurer, IME
We’ve used signals for communication for eons. One of the most famous signaling scenarios allegedly happened during the American colonies’ struggle for independence. Memorialized in the poem “Paul Revere’s Ride,” written by poet Henry Wadsworth Longfellow, the passage is quoted here:

“One if by land, and two if by sea;
And I on the opposite shore will be,
Ready to ride and spread the alarm
Through every Middlesex village and farm,
For the country-folk to be up and to arm.”


Now, there’s some question as to whether that event actually took place. One historical website mentions that this was actually a backup plan that Paul Revere mentioned in a 1798 letter to then Corresponding Secretary of the Massachusetts Historical Society, Jeremy Belknap.

Whether it happened or not, good old Paul’s plan showcases two important concepts:

  • Signals are important for warning people of impending danger, and
  • It’s not a bad idea to have a backup plan.

People can be quite unreliable at times. Automated signaling fills in the gaps.

A signal by any other name… would still do the job
Yeah, another poetic reference, this time from Willie Shakespeare. But the fact is we have signaling devices all around us, even if we don’t call them that. They might go by “alarms” or “warnings” or “indicators.”

But, they’re signals, each and every one.

Signals in one form or other are used everywhere. We’ll find them in a variety of industries:

  • Commercial/retail businesses
  • Hazardous locations
  • Industrial and manufacturing facilities
  • Marine locations, and even
  • Single or multi-unit residential housing

You do have a smoke detector in your home or apartment, right? And you are changing the batteries and testing the detectors regularly, right?

Mine get tested every time I fry up some bacon… darn it!

Of course, smoke detectors are audible signals. They’re designed to cut through the noise of everyday life and the din of the factory. In fact, it might easier to hear that alarm than see the problem happening.

Unless… you can’t hear it.

Enter the visual signal. Often in the form of beacons or strobes, they catch our eye quickly. Multi-colored stacks or towers also indicate state of operation, not just fail or run. Some are used to indicate position or readiness.

For example, I recently wired in some roll up doors that had LED warning light strips on the jamb. When getting ready to close, the LEDs flashed yellow to warn of impending operation. Right before and during the door’s closing, they flashed red.

Truck docks often use a lockable setup with indicator lights. A red light lets the trucker know that the dock door is open and the trailer is being loaded. When it’s green, the driver can pull away from the dock and get ready to head on down the highway.

A combination of audible and visual signals works best where one or the other might be unnoticed. They can be housed in separate units or combined into one device. Both a lighted beacon and a warning horn ensure that everyone understands what’s going on.

But wait… there’s more.

There are actually message centers that display text as a warning. Now the alerted person can know exactly what’s going on, not just guess at it. An annunciator and text message ensure that the right message is sent and received.

Very cool!

Applications for signaling are endless
Signaling devices are critical parts of emergency operations, like fire alarms or inclement weather warnings. In hospitals and health-care facilities, they can be used by patients to get assistance.
And on the factory floor, they can warn of machine failures.

I’d recommend that you talk with a signaling expert when designing or specifying an signaling system for your application. There may be some that are unacceptable for what you need to do. Hazardous locations need devices specifically designed to prevent catastrophes. There may be other considerations as well.

For example, a few years ago I was asked to install a warning light on a stairwell. It was green when the employee approached it and turned amber right before they climbed the stairs. Situated beside a safety sign about stairwell use, it was used to remind them to, uh, tread carefully.

The manager wanted the amber signal to flash, kind of a strobe effect to make sure they noticed. But often a strobe can trigger an epileptic seizure (said so right in the installation instructions… a document I’m sure you ALWAYS read.) Not exactly something you want to happen in a stairwell.

After showing him what the document said, he relented and went with a steady-on signal.

The key is to match the type of signal to the situation. The choices available today give you options way more effective than, well…

lanterns in a church tower.
Photo courtesy of Edwards Signaling
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