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

Allen-Bradley 1786-XT Series A ControlNet 75 Ohm Coaxial Trunk Terminator

Product Overview

The 1786-XT (Series A) is a precision-engineered 75 Ω terminating resistor designed by Rockwell Automation for the ControlNet physical layer. As a critical component for network stability, the 1786-XT is installed at both ends of a ControlNet coaxial trunk segment. Its primary function is to absorb electrical signals at the end of the line, preventing signal reflections (standing waves) that cause data corruption and intermittent communication errors. Built with a gold-plated center pin and nickel-plated housing, this terminator ensures the deterministic, high-speed performance required for distributed I/O systems and PLC synchronization in demanding industrial environments.

Technical Specifications

The 1786-XT provides a precise impedance match to maintain high signal-to-noise ratios across the network.

• Manufacturer: Rockwell Automation / Allen-Bradley

• Model Number: 1786-XT

• Series: Series A

• Type: Coaxial Terminating Resistor

• Impedance: 75 Ω (±1% tolerance for high-precision matching)

• Connector Type: BNC Plug (Bayonet Neill–Concelman)

• Frequency Range: DC to 5 MHz (Standard ControlNet operating spectrum)

• Compatible Media: RG-6 Quad-shield coaxial cable

• Housing Material: Nickel-plated brass for corrosion resistance

• Contact Material: Gold-plated center pin for maximum conductivity

• Operating Temperature: -40°C to +85°C (-40°F to +185°F)

• Storage Temperature: -40°C to +85°C

• Weight: 0.04 lbs (18 grams)

• Compliance: IECEx, CE, UL, CSA, and RoHS certified

Core Functional Features

• Reflection Suppression: The 1786-XT eliminates the "echo" effect on coaxial lines, ensuring that the high-speed 5 Mbps ControlNet signal remains clean and readable for all nodes.

• Industrial Durability: Designed for the plant floor, the nickel-plated brass construction resists oxidation and provides a secure, vibration-resistant bayonet lock.

• Signal Integrity: By maintaining the correct 75 Ω network impedance, the terminator helps prevent "Media A/B" errors on scanner modules (like the 1756-CN2B or 1756-CNB).

• Wide Thermal Range: Unlike consumer-grade terminators, the 1786-XT maintains its precise resistance value even during extreme temperature fluctuations in unconditioned enclosures.