ST-9283 RF / GPS Priority Detector

Intersections equipped with the EMTRAC system have an omni-directional UHF antenna (mounted either on a signal pole or on the traffic cabinet) and a Priority Detector, which consists of a 900-MHz spread-spectrum transceiver and a single-board computer integrated in a dual-card assembly that plugs into the traffic cabinet’s detector rack or on an interior shelf.


The Priority Detector can be installed directly into the input file of Type 170 controller cabinets or may be provided with a Priority Detector Case (ST-9194) for NEMA cabinets (when input-file space is not available).

  • Includes serial RS-232 or Ethernet communications to enable remote monitoring of system activity and configuration of EMTRAC equipment through the existing traffic network
  • Supports up to 16 inputs and 16 outputs, with one auxiliary output configurable as a GPS timing signal
  • Logs up to 5,000 locally-stored events (up to 10,000 events with removable memory)
  • Four main directional outputs and up to 12 auxiliary outputs are provided, with each input and output signal optically isolated for 2,500 volts
  • Operates on 120 VAC with its own power supply, and fits all Major NEMA and 170 Type Cabinets
  • Includes indicator lights for power on, signal received, active-output by priority, and direction of signal or channel
  • Includes toggle switches to send output in either Priority 1 or Priority 2 mode, allowing manual testing of detector function and intersection response. The Standby/Active switch enables testing and configuration without affecting live signal
  • Compatible with all major brands of NEMA and 170/2070 controllers
  • Optically-isolated outputs (and auxiliary inputs)


The ST-9283 Priority Detector includes the following connection options:

  • Card-Edge: Controller Connections
  • RJ45 Ethernet (local computer/network): 2 ports
  • USB Mini-B: Interface Computer
  • Detector-Case Rear D-Sub (shelf-mount controller connections): Up to 16 auxiliary inputs and outputs
  • 26-Pin D-Sub Serial: Controller Connections

Software Settings and Features

  • Time to Hold Request After Loss of Signal
  • Max. Request Time/Min. Request Times (by channel)
  • Priority Service (how simultaneous requests are served)
  • Activity Log Display of Most Recent Events
  • Vehicles Allowance or Denial (by vehicle ID)
  • Minimum Time Duration (Priority Detector will give an output signal for minimum amount of time)
  • Configurable Output Channels (by direction)
  • Communications Baud Rate

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