What is RS‑485? (Short Overview)
RS‑485, also known as TIA/EIA‑485, is a standard for serial communication that uses differential signaling to transmit data reliably over long distances. It’s widely used in industrial automation, building controls, and transportation systems because it can support multiple devices on the same network while resisting electrical noise. Common protocols that rely on RS‑485 include Modbus, BACnet MS/TP, CANopen, and DMX512.
Why it matters: RS‑485’s differential signaling reduces interference from motors, drives, and other machinery, making it ideal for harsh environments
Belden offers a comprehensive family of RS-485 cables designed for long-distance communication, strong noise immunity, and dependable performance in harsh or specialized environments.
Reference: Belden RS-485 Cable Family
How to Use This Selection Guide
The tables below summarize Belden’s RS-485 cable families by application type, shielding, pair count, conductor size, and jacket rating. Use these tables to quickly shortlist appropriate cable part numbers before reviewing individual data sheets for detailed electrical specifications.
Pro tip: For installations in harsh environments, check for direct-burial or armored options—even for short runs, it may save troubleshooting later.
Industrial and Harsh Applications
These RS-485 cables are engineered for industrial networks and harsh operating environments. They feature robust jackets, shielding, and in some cases direct-burial or armored constructions.
Example: On a factory floor with high electrical noise, an SF/UTP armored cable like 123108A not only prevents interference but also protects the cable from physical damage, improving overall system reliability.
| Belden Part | Shielding | Pairs (PR) | Conductor (AWG) | Jacket Type | Typical Notes |
|---|---|---|---|---|---|
| 3074F | SF/UTP | 1 | 18 | Industrial PVC | Industrial RS-485 / data in harsh environments. |
| 3105A | SF/UTP | 1 | 22 | CM/PLTC | General industrial RS-485 link. |
| 3106A | SF/UTP | 1.5 | 22 | CM/PLTC | Higher pair count for additional channels. |
| 3107A | SF/UTP | 2 | 22 | CM/PLTC | Two-pair industrial RS-485 / fieldbus. |
| 3108A | SF/UTP | 3 | 22 | CM/PLTC | Three-pair industrial RS-485. |
| 3109A | SF/UTP | 4 | 22 | CM/PLTC | Four-pair industrial RS-485. |
| 3105DB | SF/UTP | 1 | 22 | CPE, direct burial | Direct-burial industrial RS-485. |
| 3106DB | SF/UTP | 1.5 | 22 | CPE, direct burial | Direct-burial, higher pair count. |
| 3107DB | SF/UTP | 2 | 22 | CPE, direct burial | Direct-burial, two-pair RS-485. |
| 3108DB | SF/UTP | 3 | 22 | CPE, direct burial | Direct-burial, three-pair RS-485. |
| 3109DB | SF/UTP | 4 | 22 | CPE, direct burial | Direct-burial, four-pair RS-485. |
| 123108A | SF/UTP | 3 | 22 | Industrial PVC with AIA | Aluminum interlocked armor for mechanical protection. |
| 123109A | SF/UTP | 4 | 22 | Industrial PVC with AIA | Armored four-pair RS-485 for harsh environments. |
| 133105A | SF/UTP | 1 | 22 | SIA | Shipboard/industrial RS-485. |
| 133107A | SF/UTP | 2 | 22 | SIA | Shipboard/industrial, two-pair. |
| 7200A | SF/UTP | 1 | 24 | PVC | Compact RS-485 data cable. |
| 7201A | SF/UTP | 2 | 24 | PVC | Two-pair RS-485 data. |
| 7202A | SF/UTP | 3 | 24 | PVC | Three-pair RS-485 data. |
| 7203A | SF/UTP | 4 | 24 | PVC | Four-pair RS-485 data. |
Installer tip: If your run is exposed to outdoor conditions or is partially buried, consider direct-burial cables (CPE) to reduce maintenance over time.
Marine Transportation Applications
These RS-485 constructions are optimized for marine and transportation use, featuring low-smoke, halogen-free jackets and approvals common in that segment.
Tip: LSNH-rated cables like 3105T are ideal for enclosed transportation areas where fire safety is critical.
| Belden Part | Shielding | Pairs (PR) | Conductor (AWG) | Jacket Type | Typical Notes |
|---|---|---|---|---|---|
| 3105T | SF/UTP | 1 | 22 | TP LSNH | Low smoke, halogen-free RS-485 for transport |
| 3106T | SF/UTP | 1.5 | 22 | TP LSNH | Higher pair count LSNH cable |
| 3107T | SF/UTP | 2 | 22 | TP LSNH | Two-pair LSNH RS-485 |
| 3108T | SF/UTP | 3 | 22 | TP LSNH | Three-pair LSNH RS-485 |
| 3109T | SF/UTP | 4 | 22 | TP LSNH | Four-pair LSNH RS-485 |
| 3105Z | SF/UTP | 1 | 22 | LSNH | Low smoke, halogen-free variant |
| 3106Z | SF/UTP | 1.5 | 22 | LSNH | LSNH with higher pair count |
| 3107Z | SF/UTP | 2 | 22 | LSNH | Two-pair LSNH RS-485 |
| 3108Z | SF/UTP | 3 | 22 | LSNH | Three-pair LSNH RS-485 |
| 3109Z | SF/UTP | 4 | 22 | LSNH | Four-pair LSNH RS-485 |
Light Industrial Applications
Light industrial RS-485 cables feature smaller conductor sizes and a mix of PVC, plenum, and low-smoke halogen-free jackets suitable for building automation or office environments.
Installer note: For plenum spaces, always choose CMP-rated cables such as 82841 to comply with building codes.
| Belden Part | Shielding | Pairs (PR) | Conductor (AWG) | Jacket Type | Typical Notes |
|---|---|---|---|---|---|
| 9841 | SF/UTP | 1 | 24 | PVC | CMG-rated light industrial RS-485 |
| 9842 | SF/UTP | 2 | 24 | PVC | Two-pair CMG cable |
| 9843 | SF/UTP | 3 | 24 | PVC | Three-pair CMG cable |
| 9844 | SF/UTP | 4 | 24 | PVC | Four-pair CMG cable |
| 9841ZH | SF/UTP | 1 | 24 | LSNH | Low smoke, halogen-free variant |
| 9842ZH | SF/UTP | 2 | 24 | LSNH | Two-pair LSNH cable |
| 9843ZH | SF/UTP | 3 | 24 | LSNH | Three-pair LSNH cable |
| 9844ZH | SF/UTP | 4 | 24 | LSNH | Four-pair LSNH cable |
| 82841 | SF/UTP | 1 | 24 | PVC, CMP | Plenum-rated RS-485 |
| 82842 | SF/UTP | 2 | 24 | PVC, CMP | Two-pair plenum cable |
| 82843 | SF/UTP | 3 | 24 | PVC, CMP | Three-pair plenum cable |
| 82844 | SF/UTP | 4 | 24 | PVC, CMP | Four-pair plenum cable |
| 89841 | SF/UTP | 1 | 24 | FEP | High-temperature / special plenum application |
| 89842 | SF/UTP | 2 | 24 | FEP | Two-pair high-temperature cable |
How to Choose a Belden RS-485 Cable
Identify your application: industrial, marine, or light industrial. Then match conductor size, pair count, shielding, and jacket type to your environment and applicable codes.
Quick tip: Longer runs or harsh areas with high electrical noise benefit from shielded and armored cables. It may cost more upfront but saves troubleshooting later.
Always review Belden datasheets for impedance, capacitance, temperature rating, and approvals before finalizing your bill of materials.