ISO 11446:2004 specifies a 13-pole electrical connector between towing and towed vehicles with 12 volt electrical system. It was developed in 1987 by Erich Jaeger to replace older 7-pin plugs.
Notes
References
Sources Right Connections UK Limited ISO 11446 (2004) ISO 11446-1 (2012) ISO 11446-2 (2012)