ARM Series Integrated Duplex Controller

The ARM Series Integrated Duplex Controller with Intrinsically Safe Inputs from the ATC Diversified Electronics division of Marsh Bellofram is a family of rugged, high-reliability alternating relays and duplex controllers, designed to ensure equal runtime of multiple load installations in pump sequencing, level control, lift station, motor protection and other industrial applications. The series incorporates a microprocessor-based controller which evenly distributes runtime by automatically alternating designated lead and lag loads between two pump sequences.

The series also features an inrush delay, which prevents both loads from energizing simultaneously, thus significantly reducing line sag, while allowing for additional load capacity in the event of excess requirements. Units include five UL913 intrinsically safe low voltage/low current control switch inputs which are electrically isolated from the control voltage and load alarm contacts. Five LED indicators are included to confirm the functionality of the inputs. Incorporation of hand-of-automatic (H-O-A) switches allow for manual operation as needed.

Additional features include an integral alarm output, with alarm contacts that close when a control switch fails or system capacity is exceeded; control switch fault detection, which notifies the user of open and shorted control switch failures; and a test-and-clear switch, which verifies device function and resets the control switch fault detection algorithm as needed. The integral device logic of the ARM Series Integrated Duplex Controller with Intrinsically Safe Inputs allows for outputs to continue their operation, even if one input fails to open or close. Special controls are also available upon customer request. Available mounting configurations allow for back or front panel mounting, as required.



  • Microprocessor-based alternating relay
  • Designed to provide equal runtime on two loads
  • Five (5) intrinsically safe control switch inputs
  • UL913 listed device
  • Optional panel mounted versions


  • Pump sequencing
  • Level control
  • Lift stations
  • Motor protection
  • Other industrial applications