"The present document applies to the following radio equipment types: ? Very High Frequency (VHF) Digital Link (VDL) Mode 4 ground-based radio transmitters and receivers for air-ground communications operating in the VHF band@ using Gaussian-filtered Frequency Shift Keying (GFSK) Modulation with 25 kHz channel spacing and capable of tuning to any of the 25 kHz channels from 118@000 MHz to 136@975 MHz as defined in ICAO VHF Digital Link (VDL) Standards and Recommended Practices (SARPs) [2]. The present document is designed to ensure that equipment will be compatible with the relevant ICAO VHF Digital Link (VDL) Standards and Recommended Practices (SARPs) [2] and VDL Mode 4 Technical Manual (TM) [1]. The present document does not give a presumption of conformity related to maintenance requirements@ safety@ civil/military coordination or environmental constraints. NOTE: For these ERs@ please refer to the Local Air Navigation Service Provider procedures. Manufacturers should note that in future the tuning range for the ground transceivers may also cover any 25 kHz channel from 108@000 MHz to 117@975 MHz. The scope of the present document is limited to ground stations. The equivalent specification for airborne stations is EN 302 842-1 [i.5]@ EN 302 842-2 [i.6]@ EN 302 842-3 [i.7]@ EN 302 842-4 [i.8].and TS 102 842 [i.9]. The VDL Mode 4 system provides digital communication exchanges between aircraft and ground-based systems and other aircraft supporting surveillance and communication applications. The supported modes of communication include: ? broadcast and point-to-point communication; ? broadcast services including Automatic Dependent Surveillance - Broadcast (ADS-B)@ Traffic Information Service - Broadcast (TIS-B) and Flight Information Service - Broadcast (FIS-B) capabilities; ? air-air@ air-to-ground@ and ground-to-air services; ? operation without ground infrastructure. The present document is derived from the specifications: ? VDL Mode 4 standards produced under the auspices of the International Civil Aviation Organization (ICAO) [1] and [2]. ? Other relevant standards as defined in clause 2. It is envisaged that manufacturers may provide equipment supporting: ? broadcast services only; ? point-to-point services only; ? both broadcast and point-to-point services. The present document includes: ? clause 2 provides references to relevant documents; ? clause 3 provides general definitions@ abbreviations and symbols used; ? clause 4 refers to a general description and architecture of VDL Mode 4 contained in EN 301 842-2 [5]; ? clause 5 provides tables tracing technical requirements specifications applicable to the interoperability Regulation [i.4]; ? annex A provides a Bibliography; ? a document history. Mandating and Recommendation Phrases a) ""Shall"" The use of the word ""Shall"" indicates a mandated criterion; i.e. compliance with the particular procedure or specification is mandatory and no alternative may be applied. b) ""Should"" The use of the word ""Should"" (and phrases such as ""It is recommended that...""@ etc.) indicate that though the procedure or criterion is regarded as the preferred option@ alternative procedures@ specifications or criteria may be applied@ provided that the manufacturer@ installer or tester can provide information or data to adequately support and justify the alternative."