Signaling Devices

Quick Tips #380

Signaling devices can be comprised of a variety of different styles, colors and shapes and are used for many different purposes. Signaling typically consists of lights combined with a variety of sound producing products. This article will explore signal lights, their different uses, makeup and terminology.

Signal lights are used in many different situations. They are used to signal the status of machinery, conveyors, and automated lines using different colors to show the status from a distance. Other uses are for visibility of emergency vehicles, school buses, snow plows, wreckers, slower moving construction vehicles, such as end loaders and graders, and are commonly used in conjunction with back-up alarms on fork trucks. Entrances and exits in loud environments use signal lights as a way to warn of hazardous environments and dangerous areas. The lights are designed for indoor and indoor/outdoor use.

Applications and other aspects of a signaling system need to be considered when purchasing signaling lights. Different applications may call for different bulb types, voltage and colors as well as how the light is going to be mounted.

There are several choices when choosing the type of signaling light and bulb to be used. The most common choices are: strobe lights, which use a strobe tube or more commonly an LED lamp, rotating flash, which typically use incandescent or Halogen flash tubes and LED or stack type lights. Strobe lights have bright rapid flashes (typically 90 flashes per minute) and are highly visible at night, in fog and are also low maintenance. A rotating or revolving light rotates approximately 60 times per minute. These are more visible in bright sunlight, have a greater visibility over distance and have longer "on time" to the human eye. LED's, which are becoming more and more common, are bright, stay cool to the touch and may last for thousands of hours. Most lights can be set up as a flasher or light up in a variety of different patterns. Stack lights, which can be stacked in different color combinations, light up and can stay on or blink to show status, depending on the need.

Just as in traffic control signal lights, the signal device lens colors have meaning. The Society of Automotive Engineers' standard, SAE J578 specifies the colors used for signaling devices.

Signal lights for use on vehicles or moving equipment meet certain ratings defined by the SAE. These lights are rated and defined by class. Each class is defined by specific photometric criteria for flash brightness and distribution:

  • Class I: signal device for emergency use on emergency vehicles
  • Class II: warning light for maintenance/service vehicles to warn of traffic hazards
  • Class III: warning device for identification only

Voltage is another determining factor for the type of signaling light needed. If the signal light is going to be wired into a facility, it would need to be 115-120 volt AC. Other voltages are available, such as 24 volt AC, which are used in facilities that use a transformer to reduce voltage from 120 to 24 volts. These offer different amperage options to meet a facility's needs. Other options for signal lights are 12 to 48 volts DC. If the light is to be wired into a vehicle or other 12 volt battery system, the light would need to be 12 volt DC. Some lights for vehicles come with plug adaptors and magnets for ease of attachment and portability. All of the others need to be integrated into the vehicles wiring system or fuse box.

Depending on the light type, there can be different mounting options. The more common mount types available are surface mount and pipe mount and magnetic or permanent mounts for vehicles.

Sources for More Information

Society of Automotive Engineers (SAE)

Federal Signal


Find even more information you can use to help make informed decisions about the regulatory issues you face in your workplace every day. View all Quick Tips Technical Resources at

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Please Note:
The information contained in this publication is intended for general information purposes only and is based on information available as of the initial date of publication. No representation is made that the information or references are complete or remain current. This publication is not a substitute for review of the current applicable government regulations and standards specific to your location and business activity, and should not be construed as legal advice or opinion. Readers with specific questions should refer to the applicable standards or consult with an attorney.

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