The standard ISO 1185 for trailer connectors was developed in the early 70s to create a standard in the commercial vehicle industry for the electrical connection between towing vehicle and trailer. The first version of the standard dates back to 1975. The latest revision is from 2003. Its purpose is to transfer the lighting signals from the drivers cab to the trailer. This also includes signals for the trailer brake control. The standard incorporates plugs, sockets and cables.

Two types of 7-pin 24V connectors

The standard has the addition "Type N" for "normal". There is also a "Type S" for 7-pin 24V trailer connectors which is defined in the standard ISO 3731. The "S" stands for "supplemental" as Type S connectors transfer additional functionalities - for example steady plus for the power supply of a trailer. For a better recognizability, the "normal" system features a black housing for plug and socket while the housing of the supplementary system is white. Due to a different contact arrangement whithin the connectors, users can not accidentally plug a normal plug into a supplementary socket and vice versa.

Application of ISO 1185 Type N

Connectors according to ISO 1185 can only be used for simple trailers because the 7 pins can only transfer the most basic lighting functions. This does not cover the reversing and rear fog light so if one or both of these lights are mandatory, the driver has to use either a second 7-pin connector (ISO 3731) or a 15-pin connector (ISO 12098). The same applies for towing a trailer which needs a power supply.

Scope of ISO 1185 Type N

The standard ISO 1185 specifies the dimensions of, and contact allocation tests and requirements for, 7-pole connectors of type 24N for the electrical connection of towing and towed vehicles with 24 V nominal supply voltage, thus ensuring interchangeability.