This International Standard specifies the dimensions of, and gives particular requirements for, 7-pole connectors of type 24 N and their contact allocation for the electrical connection of towing and towed vehicles with 24 V nominal supply voltage, thus ensuring interchangeability. NOTE For new developments and where more than 7 poles are required, as an alternative to the use of the 7-pole connector in accordance with this International Standard and ISO 3731, the use of the 15-pole connector in accordance with ISO 12098 may be required