ART1 – 3 – ARTICLE 1 Terms and definitions Section I – General terms MOD 1.14 Coordinated Universal Time (UTC): Time scale, based on the second (SI), as described in Resolution 655 (WRC-15). (WRC-15) Section IV – Radio stations and systems ADD 1.108A meteorological aids land station: A station in the meteorological aids service not intended to be used while in motion. (WRC-15) ADD 1.108B meteorological aids mobile station: A station in the meteorological aids service intended to be used while in motion or during halts at unspecified points. (WRC-15) ARTICLE 2 Nomenclature Section I – Frequency and wavelength bands MOD 2.1 The radio spectrum shall be subdivided into nine frequency bands, which shall be designated by progressive whole numbers in accordance with the following table. As the unit of frequency is the hertz (Hz), frequencies shall be expressed: – in kilohertz (kHz), up to and including 3 000 kHz; – in megahertz (MHz), above 3 MHz, up to and including 3 000 MHz; – in gigahertz (GHz), above 3 GHz, up to and including 3 000 GHz. However, where adherence to these provisions would introduce serious difficulties, for example in connection with the notification and registration of frequencies, the lists of frequencies and related matters, reasonable departures may be made1. (WRC-15)