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A Technical Look Inside ATC Cabinets

 Traffic cabinets have remained pretty much unchanged for over 30 years. That is until the ATC cabinet hit the market and changed the game, combining the best of rack mount and serial-based designs. But new and different doesn’t have to mean intimidating and scary. In this special tech edition of The Source we look at what differentiates these cabinets and why there is no reason to hide from change.

Working Smarter, Not Harder
Doing more with less should be the slogan of the ATC cabinet series. With high-density components such as the switch pack, flasher, cabinet monitor unit (CMU), and flash transfer relay (FTR), ATC cabinets optimize cabinet space for increased capabilities using half the space.ATC-cabinet_extra-space

ATC cabinets are also the first that come in two versions; either 120 VAC or 48 VDC power. DC power has the ability to improve operational efficiencies, increase cost savings, and boost safety for drivers, personnel, and the public.

The Nuts and Bolts 
Traffic cabinets house the components that transfer information to and from the controller and help manage traffic. ATC cabinets achieve all of that and more, with smarter and more efficient parts. Below are some of the changes and improvements made to make managing any traffic scenario easier than ever.


  • Supports 120 inputs
  • Field Input Termination Assembly (FITA): This 24- or 48-channel panel is used to terminate field input loop wires, PPB wires, EVP wires, etc.
  • Input Assembly: Houses detection modules, isolator cards, SIU, etc.
  • 24-Channel Input Assembly: Houses twelve 2-channel devices, or six 4-channel devices, or a combination of two 4-channel devices
  • 48-Channel Input Assembly: Houses twelve 4-channel devices or a combination of 2 and 4-channel devices


  • Supports 3Inputs_Outputs_CMU22 outputs
  • Field Output Termination Assembly (FOTA): 16-Channel assembly used to terminate field lamp wires
  • Output Assembly: Houses high-density switch packs, CMU, and SIU
  • 16-Channel Output Assembly: Houses eight high-density switch packs
  • 32-Channel Output Assembly: Houses sixteen high-density switch packs


  • The EDI CMUip-2212 is a compact and modular cabinet malfunction management system.
  • Capable of monitoring up to 32 physical switch pack channels (RYG). An optional four virtual channels can be used to optimize compact applications.
  • Using the load current information from the iPack® 2202 switches, a dark intersection that results from a no-load condition can be detected at the time of the fault rather than waiting for the signal to cycle. The diagnostic wizard uses load current information to unambiguously diagnose open load and leakage faults.

Lessons Learned
While deploying these powerful cabinets, we have learned a great many things, here are a few of those gems to make your transition as seamless as possible.


Before an ATC cabinet is deployed in the field, it is recommended that the CMU/Datakey and controller are programmed per intersection configuration. Run the ATC cabinet with full load, simulating the intersection at the lab to assure a safe and smooth turn-on.


When deploying a DC cabinet keep note that auxiliary equipment, such as a preempt confirmation light, will also need to be converted to DC power.


ATC cabinets have an open architecture meaning that they support controllers from other companies. If you choose to use another brand of controller be sure to have a firm understanding of how the I/O mapping is accomplished.


ATC cabinets have made quite the splash since entering the market and are only picking up momentum as time goes on. To get a better understanding register for our next webinar, “A Technician’s Guide to ATC Cabinets,” and remember we’re here to help! So contact us today if you have any questions or inquiries.


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