This part of IEC 61097 specifies the minimum operational and performance requirements and methods of testing with required test results for transmitters and receivers capable of voice communication, digital selective calling and narrow band direct printing telegraphy for the GMDSS operating in either the medium frequency band only or in medium and high frequency bands allocated in the ITU Radio Regulations to the Maritime Mobile Service, as required by Chapter IV of SOLAS 1974 as amended in 1988 and which is associated with IEC 60945. When a requirement in this standard is different from IEC 60945, the requirement of this standard shall take precedence. This standard refers to equipment for: – single side-band (SSB) transmission and reception for radiotelephony; – frequency shift keying or single side-band transmission and reception for digital selective calling signals (DSC) according to Recommendation ITU-R M.493-7; and – frequency shift keying or single side-band transmission and reception for narrow band direct printing telegraphy (NBDP) according to Recommendation ITU-R M.625-3; as applicable. This standard refers to radio equipment, which is not integrated with DSC encoders or decoders, or NBDP modems, but defines the interfaces with, and the RF characteristics of, such equipment. NOTE – The requirements for integrated DSC encoders or decoders may be found in IEC 61097-3 and for integrated NBDP modems in the future IEC 61097-11. These requirements include the relevant provisions of the Radio Regulations and of the IMO Resolutions A.334(IX), A.421(XI), A.694(17), A.804(19), and A.806(19) and SOLAS. NOTE – The requirement for two-tone generators (A.421(XI)) is only applicable until 1 February 1999. If the equipment, or parts of it, is designed in such a manner that it can be used for other categories of maritime radiocommunication services (e.g. radio data or facsimile transmission), those parts of the equipment shall fulfil the relevant requirements of the appropriate standards for the service(s) in question. NOTE – All text of this standard the wording of which is identical to that in IMO Resolutions and to that in the relevant ITU-R Recommendations is printed in italics and is prefixed by references (804 etc.) in brackets. When the text is identical in A.804 and A.806 the reference A.806 will be used.