IEC 61156-12:2025

Overview

IEC 61156-12:2025 is the IEC sectional specification for symmetrical single pair cables used in work area wiring for digital communications. It defines transmission characteristics up to 1.25 GHz (measured at 20 °C) and covers both unscreened and screened single balanced pair cabling intended for office, home and industrial applications referenced in ISO/IEC 11801-1:2017 and its amendment. This second edition (2025) updates the 2021 edition by adding a higher-performance cable type (T1‑C) and introducing low frequency coupling attenuation as a screening-efficiency parameter.

Key topics and technical requirements

IEC 61156-12:2025 specifies electrical, mechanical and environmental requirements, including:

• Cable types and frequency ranges
  • T1‑B: 0.1 MHz – 600 MHz
  • T1‑C: 0.1 MHz – 1.25 GHz (new in 2025 edition)
• Transmission characteristics
  • Attenuation, phase/delay and velocity of propagation, impedance and return loss
  • Unbalance parameters (TCL, EL TCTL) and pair-to-pair crosstalk
  • Alien (exogenous) near‑end and far‑end crosstalk (PS ANEXT, PS AACR‑F)
• Screening performance
  • Transfer impedance and coupling attenuation
  • Low frequency coupling attenuation (new integral screening parameter below 30 MHz)
• Electrical tests
  • Conductor resistance, resistance unbalance, mutual capacitance, dielectric strength, insulation resistance
• Mechanical and environmental tests
  • Bending radius, tensile and elongation tests, crush/impact, temperature ageing, damp heat, UV, wicking, flame and smoke characteristics
• Bundled cable requirements
  • NEXT, ACR‑F and bundled behaviour for multiple pairs in one sheath
• Informative annex
  • Blank detail specification (Annex A) and background (Annex B)

Applications and intended users

IEC 61156-12:2025 is intended for:

• Cable manufacturers designing and qualifying symmetrical single pair products (T1‑B, T1‑C)
• Network designers and system integrators specifying work area cabling for high-speed single-pair Ethernet or similar digital services (e.g., 1000BASE‑T1 referenced)
• Test laboratories and certification bodies performing verification and compliance testing
• Procurement and specification writers in office, home and industrial environments

The standard helps ensure predictable electrical performance, screening effectiveness, mechanical durability and environmental robustness for modern single-pair digital applications.

Related standards

• ISO/IEC 11801-1:2017 (generic cabling for work area wiring)
• ISO/IEC TR 11801 9906 (example application: 1000BASE‑T1)
• Other parts of IEC 61156 series covering multicore and pair/quad cables

Keywords: IEC 61156-12:2025, single pair cables, 1.25 GHz, T1-C, work area wiring, coupling attenuation, transfer impedance, ISO/IEC 11801.