Allen Bradley 1786-XT ControlNet 75-Ohm BNC Network Terminator

Product Overview

The Allen Bradley 1786-XT serves as a critical component for maintaining the integrity of a ControlNet coaxial network. This 75-Ohm BNC terminator absorbs electrical signals at the physical ends of the trunk cable, preventing signal reflection that causes data corruption. We supply this unit in 100% Brand New original condition to ensure your high-speed deterministic network operates without communication faults or packet loss.

Technical Specifications

The 1786-XT matches the characteristic impedance of standard ControlNet RG-6 coaxial cables to provide a clean electrical termination.

Engineering Advantages

• Eliminates Signal Reflection: The 1786-XT absorbs the wave energy at the end of the cable run. This prevents the signal from bouncing back down the line, which otherwise creates standing waves and disrupts communication for all nodes on the segment.

• Maintains 75-Ohm Impedance: This terminator precisely matches the 75-ohm requirement of the ControlNet specification. Using an incorrect resistance (such as standard 50-ohm video terminators) introduces impedance mismatches that degrade network performance.

• Standardized BNC Interface: The twist-lock BNC connector ensures a secure physical connection to the ControlNet tap. The mechanical locking mechanism resists loosening caused by cabinet vibrations or thermal expansion.

• Essential for High-Speed Logic: At 5 Mbps, ControlNet timing remains ultra-sensitive. The 1786-XT ensures the physical layer remains stable, allowing the processor to maintain precise Network Update Times (NUT) without retries.

FAQs

• Where exactly do I install the 1786-XT?

  You must install a 1786-XT terminator on the open BNC port of the taps located at the two extreme ends of the ControlNet trunk cable. A standard network segment requires exactly two terminators—one at each end.

• Can I use a standard 50-ohm BNC terminator instead?

  No. ControlNet requires 75-ohm termination. Using a 50-ohm terminator creates an impedance mismatch that generates significant network errors and may prevent nodes from joining the network entirely.

• How do I verify if the terminator is functioning correctly?

  With the network powered down and the terminator removed from the tap, use a digital multimeter to measure the resistance between the center pin and the outer shell. It should read approximately 75 ohms.

• Is this a genuine Allen Bradley part?

  Yes. We provide only 100% Brand New original Allen Bradley 1786-XT terminators. Genuine terminators use high-tolerance internal resistors designed to withstand industrial temperature cycles without drifting from the 75-ohm specification.