单项选择题 All ships which, in accordance with the present Convention, are required to carry radio installations shall carry（）.

单项选择题 Digital Selective Calling means a technique using（）which which enables a radio station to establish contact with, and transfer information to another station or group of stations and complying with the relevant recommendations of the CCIR.

单项选择题 （）means a technique using digital codes which enables a radio station to establish contact with, and transfer information to another station or group of stations and complying with the relevant recommendations of the CCIR.