Electronic and Postal Communications (Radio communications and Frequency Spectrum) G.N. No. 424 (contd) licence upon passing the radio amateur examination set by the Authority or be in possession of an Amateur radio certificate acceptable to the Authority. Prohibiti-on on use of encryption devices 21. Any amateur station licensee shall not make use of encryption devices or equipment in the operation or use in any station. Restrictions on transmissions 22.-(1) Any message transmitted through an amateur station shall be in plain language and relate solely to amateur services. (2) Any amateur station shall not be used for transmitting news, advertisements and communications of a business nature or of non experimental character, messages for monetary reward or messages for or on behalf of a third party. (3) Except with the written permission of the Authority, a licensee of an amateur station shall not call or transmit to any station other than an amateur station. (4) Transmission shall not commence without listening in the frequency to be used in order to ascertain that no interference is likely to be caused to any other station which is in operation.. (5) Any amateur radio station shall not transmit powers exceeding 100W. Power of the authority to order transmission 23. The Authority may, in case of natural disaster, by notice in writing require the licensee to transmit any message by means of its licensed amateur station. Portable station 24. The Authority may approve an amateur station as a portable or mobile stations, subject to such conditions as the Authority may prescribe. Experimental station licence 25.-(1) licence to - The Authority may grant an experimental 136