Historical
IEC 61156-1 Ed. 3.1 b:2009
Multicore and symmetrical pair/quad cables for digital communications - Part 1: Generic specification
"IEC 61156-1:2009, consolidated version, consists of the third edition (2007) and its amendment 1 (2009). The technical content is therefore identical to the base edition and its amendment and has been prepared for user convenience. It bears the edition number 3.1"
Content Provider
International Electrotechnical Commission [iec]