1.1 This European Standard establishes the requirements and tests applied to safety switching devices for limiting the pressure - here after called devices - to ensure that the maximum or minimum pressure, which is caused by a pressure generator in refrigerating systems and/or heat pumps, is maintained within the limits of the refrigerating system and/or heat pump. These devices are of special construction equipped with mechanically operated output contacts. NOTE: Devices may be wired directly into the control circuit of the compressor or may be connected through a relay or microprocessor/computer. Transducers/analogue devices are not covered by this standard. If more stringent specifications for special applications are necessary, these should be agreed between the customer and the manufacturer of the devices. 1.2 Different safety and control functions can be combined in one device. 1.3 This standard does not apply to devices used for control purposes.