Allen-Bradley 1770-CD Industrial Network Cable – Data Highway Plus

Allen-Bradley 1770-CD Twinaxial Cable: Signal Backbone for Data Highway Plus Networks

The Allen-Bradley 1770-CD is a purpose-engineered twinaxial cable designed exclusively for Data Highway Plus (DH+) serial communication networks deployed across Rockwell Automation PLC architectures. Within a DH+ topology, the physical medium is not a passive conductor — it is an active determinant of network timing, signal fidelity, and bus arbitration reliability. The 1770-CD addresses each of these parameters through a precisely specified electrical geometry that sustains the 78 Ω characteristic impedance required by the DH+ protocol stack.

DH+ operates as a token-passing network at selectable baud rates of 57.6 Kbps, 115.2 Kbps, or 230.4 Kbps, depending on total trunk length and node count. At 57.6 Kbps, the standard maximum trunk length is 3,048 m (10,000 ft); at 230.4 Kbps, this contracts to 762 m (2,500 ft). The 1770-CD cable’s controlled impedance and low-loss dielectric ensure that signal reflections at these distances remain within the protocol’s noise margin budget — a parameter that generic coaxial or shielded twisted-pair substitutes routinely violate, producing intermittent CRC errors and token-loss events that are notoriously difficult to diagnose at the application layer.

The cable’s twinaxial geometry — two insulated conductors sharing a common foil-plus-braid shield — provides a differential signal path that inherently rejects common-mode noise. In industrial environments where variable-frequency drives (VFDs), motor starters, and high-current bus bars generate broadband electromagnetic interference, this common-mode rejection is not optional. The 1770-CD’s shield coverage exceeds 95%, achieved through the combination of an aluminized polyester foil (100% coverage) and a tinned copper braid (approximately 85–90% optical coverage). The foil handles high-frequency EMI suppression; the braid provides low-impedance ground continuity at power-line frequencies and mechanical protection against shield discontinuity during cable flexing.

The PVC outer jacket, rated for a continuous operating temperature range of −20 °C to +60 °C, is formulated for flexibility in cold-storage and outdoor-conduit installations while maintaining dimensional stability in high-ambient-temperature panel environments. The blue jacket color is a Rockwell Automation convention that allows field technicians to visually distinguish DH+ trunk cable from DeviceNet (black), ControlNet (orange), and Ethernet (grey/yellow) media — a practical detail that reduces mis-termination errors during maintenance and expansion work.

Real-time Stock & RFQ: [email protected] | WhatsApp: +86 18359268345

Technical Parameters

Hardware Logical Analysis

The 1770-CD’s electrical architecture reflects the deterministic timing requirements of the DH+ token-passing protocol. In a token-passing bus, every node must transmit within a bounded window after receiving the token; any signal distortion that causes a receiving node to misinterpret the token frame forces a network-wide timeout and re-arbitration cycle. The 1770-CD’s controlled 78 Ω impedance, matched to the DH+ transceiver output impedance, minimizes the reflection coefficient at each node tap — keeping reflected energy below the protocol’s 200 mV noise margin threshold even at maximum trunk length.

The foil-plus-braid shield architecture addresses two distinct EMI coupling mechanisms. Capacitive coupling from nearby high-voltage conductors is attenuated by the foil’s continuous coverage, which presents a low-impedance path to ground for induced displacement currents. Inductive coupling from high-current loops — the dominant interference source near motor drives — is suppressed by the braid’s low-resistance ground return, which reduces the shield transfer impedance at frequencies from 10 kHz to 10 MHz. The combination achieves a shield effectiveness exceeding 60 dB across the DH+ signal band, sufficient to maintain BER (bit error rate) below 10⁻⁹ in IEC 61000-4-3 Class 3 electromagnetic environments.

The 20 AWG stranded conductor geometry balances two competing requirements: low DC resistance for voltage drop across long trunk runs, and mechanical flexibility for installation in cable trays and conduit. Stranding also distributes mechanical stress across multiple filaments, preventing the work-hardening and eventual fracture that solid conductors experience in vibration-intensive environments such as press lines and compressor rooms. The individual conductor insulation material (typically FEP or cross-linked polyethylene in OEM production) maintains dielectric constant stability across the operating temperature range, preventing impedance drift that would otherwise shift the cable’s electrical length and alter signal propagation delay — a parameter that affects DH+ timing margin at high baud rates.

System Integration Benefits

• Deterministic token-passing latency: The 1770-CD’s controlled propagation velocity (nominally 78% of the speed of light) allows network designers to calculate worst-case token rotation time with engineering precision, supporting IEC 61131-3 scan-cycle budgeting in safety-critical loops.
• Zero-reconfiguration node addition: The cable’s 78 Ω impedance matches the DH+ tap specification, allowing new nodes to be added to an existing trunk without re-termination or impedance recalculation — reducing planned maintenance windows.
• Diagnostic transparency via RSLinx Classic: Proper cable impedance ensures that RSLinx Classic’s node health diagnostics accurately reflect device status rather than cable-induced CRC errors, reducing false-positive fault isolation time.
• Compatibility with 1770-XC connector kits: The 9.5 mm OD is dimensioned for the 1770-XC tap connector’s strain-relief clamp, ensuring mechanical retention force meets Rockwell’s 45 N pull-out specification without jacket deformation.
• Coexistence with high-power equipment: The 60 dB shield effectiveness allows DH+ trunk routing within 150 mm of 480 V motor feeder conduit — a common constraint in retrofit projects where cable tray space is limited.
• Long-run signal integrity at 57.6 Kbps: At maximum trunk length (3,048 m), the cable’s ≤ 50 pF/m capacitance limits total trunk capacitance to approximately 152 nF — within the DH+ driver’s specified load capability, preserving rise-time margins.
• Thermal stability in high-ambient enclosures: The PVC jacket’s +60 °C continuous rating accommodates installation in NEMA 12 enclosures with internal ambient temperatures elevated by drive heat dissipation, without jacket plasticizer migration that would alter dielectric properties.
• Backward compatibility with legacy 1771 and 1785 platforms: The 1770-CD is the specified medium for PLC-5 (1785), SLC 500 (1747), and MicroLogix DH+ ports, providing a single cable standard across multi-generation installed bases — simplifying spare-parts inventory management.

Quality Assurance & Global Logistics

Every 1770-CD unit supplied by siemensplc.com is sourced through verified industrial distribution channels with full traceability to Allen-Bradley / Rockwell Automation manufacturing records. Pre-shipment inspection covers label authenticity, date code consistency, jacket integrity, and impedance spot-check using a time-domain reflectometer (TDR) — the same instrument used by network commissioning engineers to verify installed cable quality. A 12-month warranty covers manufacturing defects in materials and workmanship from the date of shipment.

Logistics operations are managed from Xiamen, China, a major southeastern port city with direct access to international express and freight networks. Standard in-stock orders are dispatched within 1–3 business days via DHL Express, FedEx International Priority, or UPS Worldwide Expedited, with door-to-door transit times of 3–7 business days to North America, Europe, and Southeast Asia. For bulk cable orders (full reels or multi-reel quantities), sea freight consolidation is available with competitive lead times. All export documentation — commercial invoice, packing list, certificate of origin, and material safety data sheet — is prepared in compliance with destination-country import requirements. Emergency sourcing for unplanned plant shutdowns is handled on a priority basis; contact the sales team directly via WhatsApp for same-day response.

Contact Information

📧 Email: [email protected]
💬 WhatsApp: +86 18359268345
🌐 Web: siemensplc.com
📍 Location: Xiamen, China
© 2026 siemensplc.com. All rights reserved.