(b) 1 a contiguous set of GSM channels equal to 50% of the total available channels in the 900 MHz band, as directed by the Authority. 2 a contiguous set of GSM channels equal to 66.67% of the total available channels in the 1800 MHz band, as directed by the Authority. A User of frequencies who has complied with the provision of paragraph (a) of this Article shall have the right to such pro rata rebate of the annual fee that it has paid as is proportionate to the period of use remaining. ARTICLE 48 COMPLIANCE WITH INTERNATIONAL TREATIES AND OTHER LEGISLATION In exercising the powers provided for in this chapter, the Authority shall comply with the obligations arising from international treaties to which the Kingdom is a party and the provisions of legislation regulating air and maritime traffic and meteorology. ARTICLE 49 PREVENTING HARMFUL INTERFERENCE WITH RADIOCOMMUNICATIONS No Person shall unlawfully use any Telecommunications Equipment for the purpose of causing harmful interference with any communications or continue to cause such harmful interference after receipt of an order from the Authority to cease such interference unless such interference is caused by force majeure or emergency or rescue operations. ARTICLE 50 OBLIGATIONS OF A FREQUENCY LICENSEE Without prejudice to any condition contained in any Frequency License: 1 The operation of a Telecommunications Network that uses radio frequency spectrum is the sole responsibility of the relevant Licensee. 2 The Frequency Licence holder and its employees and agents may not use a secret sign or code in messages and conversations over the Telecommunications Network in contravention of the provisions of this Law and the regulations issued for the enforcement of this Law. ARTICLE 51 MODIFICATION AND REVOCATION OF A FREQUENCY LICENCE (a) Subject to the provisions provided for in Article 34 of the Law, the Authority may modify the conditions of a Frequency Licence. (b) The Authority shall have the right to revoke a Frequency Licence before the expiry of its term in any of the following cases: -36Translation dated 12 April 2009 This is an unofficial translation of the Law. It is provided for information purposes only. Reliance may only be placed upon the official Arabic version of the Law published in the Official Gazette of the Kingdom of Bahrain. Any comments on this translation will be gratefully received by the Authority. Please email any comments to: contact@tra.org.bh