The Allen-Bradley 1746-IO8, also cataloged as the 1746IO8 Digital I/O Cards, operates as a dedicated hardware component for discrete signal acquisition and relay switching within programmable logic controller networks.

Part Nomenclature and Catalog Mapping

• 1746-IO8: Primary catalog designation for the combination module
• 1746IO8: Standard manufacturer part string without separator hyphens
• 1746-IO8/: Alternative revision suffix marker for alternate stock tracing

Hardware Specifications

Backplane Network Velocity and I/O Scaling

The module communicates via the SLC 500 backplane bus communication velocity framework, establishing deterministic data transfer intervals between the physical terminals and the central processing unit. Backplane bus communication velocity handles discrete state updates within fixed scan cycles, preserving loop timing synchronization across distributed rack expansions. I/O density scaling allows seamless integration alongside specialized analog and communication modules without violating backplane current loading limits or introducing protocol conversion latencies. Firmware flash compatibility is managed through system software tools to maintain baseline operational stability across revision changes.

Ordering Information

• 1 x Allen-Bradley 1746-IO8 Combination Input/Output Module
• 1 x Removable Field Wiring Terminal Block Block
• 1 x Technical Hardware Reference Leaflet

Physical Installation Guidelines

• Chassis Slot Insertion
  • Ensure system rack power is fully isolated before mounting or dismounting the module to prevent backplane bus damage.
  • Align the circuit board evenly with the internal chassis guide rails and push firmly until the locking latches snap into position.
• Field Wiring Terminations
  • Strip field conductors to recommended lengths and insert them securely into the removable terminal block screw terminals.
  • Verify that high-voltage AC input lines are separated from low-voltage control loops to reduce electromagnetic interference.

Frequently Asked Technical Inquiries

• Q: What is the total channel breakdown provided by this module?
• A: The unit provides 4 discrete inputs and 4 relay outputs.
• Q: What is the specified operating voltage range for the input channels?
• A: The input circuits operate within a range of 85 Volts AC to 132 Volts AC.
• Q: What is the signal delay timing for input and output state changes?
• A: The signal delay spans between 35 milliseconds and 45 milliseconds.
• Q: What is the maximum current rating per output point at 24 VDC?
• A: Each output point delivers up to 1.2 amps at 24 VDC.
• Q: Does this hardware component support live hot-swapping inside an active rack?
• A: No, power must be cut from the chassis backplane prior to inserting or removing the module.
• Q: What are the physical dimensions of the shipping package?
• A: The shipping dimensions measure 14 cm x 13 cm x 3.3 cm.
• Q: How much does the packaged hardware unit weigh?
• A: The total unit weight is 0.2 kg.
• Q: Why is proper grounding important for the terminal wiring?
• A: Proper grounding prevents ground loops and suppresses electrical noise from disrupting digital signal integrity.