This part of EN15437 defines the minimum characteristics for the interface between a trackside Hot Axlebox Detector (HABD) and Rolling Stock (RST) that comply with the European Directives for Interoperability to ensure that the minimum functional requirement of the interface is achieved. The minimum requirements of the interface apply to: a) Rolling stock conforming to standard European railway gauge, that is 1435mm; b) Rolling stock axles fitted with outboard bearings; NOTE The design of rolling stock axles fitted with inboard bearings should respect the requirements set out in Note 2 of 5.2. c) Rolling stock with a maximum operational speed of up to and including 250 km/h; NOTE 1 That is conventional rail and class 2 high speed rail rolling stock as defined in the rolling stock TSIs. NOTE 2 Interoperable rolling stock designed for speeds above 250km/h (class 1 high speed rolling stock) are mandated to have on-board equipment for axlebox condition monitoring. The requirements for on-board equipment are described in part 2 of this standard which is currently under development. NOTE 3 Interoperable rolling stock designed for speeds above 250km/h (class 1 high speed rolling stock) are outside the scope of this Part of the standard. However, if class 1 high speed trains are required to be monitored by HABDs their target area should comply with the requirements specified in this standard, except where stated otherwise. d) Trackside HABDs that are required to monitor conventional rail and class 2 high speed rail rolling stock. The rolling stock requirements of the interface are described in Clause 5 and for the HABD requirements of the interface are described in Clause 6.