(4) The Commission may impose any conditions on the use of the assigned frequencies 19. (1) All licensees assigned the use of frequencies or frequency bands shall - Obligations of the licensee. (a) maintain and provide, at the Commission’s request, an inventory of frequencies assigned; (b) keep the license in force by regular payment of annual fees as may be prescribed from time to time by the Commission; and, (c) guard against unauthorized emission, harmful interference or illegal use of the spectrum. (2) The Commission may where it considers expedient so to do require a licensee to migrate to a new frequency band. 20.(1) A frequency licence shall not confer any ownership rights of the frequency to the licensee. Ownership of frequencies. (2) The commission may require licensees to share a frequency band. Transfer and assignment of station authorisation. Temporary authorization. Change in equipment. 21. Frequencies assigned to be used by a licensee and the rights therein granted by such authorisation shall not be transferred, without the written consent of the Commission. 22. The Commission may at its discretion grant a temporary frequency assignment. 23.(1) No material change may be made in a licensed station, including change of station parameters as specified in the license without written authorisation from the Commission. (2) Without prejudice to the generality of this regulation, a licensee shall seek the approval of the Commission where such licensee proposes a change which is likely to increase the height of a structure supporting the 25