This European Standard defines the constructional and operational characteristics, the safety requirements and test methods, and the marking of automatic change over devices with a capacity of less than or equal to 100 kg/h and having a maximum regulated pressure of less than or equal to 4 bar for butane, propane or their mixtures only in the vapour phase. NOTE 1 bar = 105 Pa. Liquefied gases containing methylacetylene and propadiene are not covered by this standard. This European Standard also covers safety devices likely to be fitted onto automatic change over devices. The characteristics of these devices are given in annex A. The requirements of this European Standard generally cover designs where regulation is in one stage, using a single diaphragm. These requirements do not exclude designs using more than one diaphragm, provided that these diaphragms are integrated in a single automatic change over devices complying with the requirements of this European Standard. For specific uses in caravans and leisure vehicles, the automatic change over devices function may also be carried out by an assembly of regulators, forming a "automatic change over devices system" as defined in 3.1.2. This standard covers such an assembly as follows: -- special requirements for the manufacture, adjustment and operation of regulators forming a automatic change over devices system, as well as the corresponding test methods are given in annex B; -- except for these special requirements, and unless otherwise stated, constructional and performance characteristics given in the body of the standard are also applicable to the devices in annex B.