right a control word is supplied to the transport block 4 subsequently in the transport block 4 there is executed a process of deciphering or descrambling the conditional access data by the use of such a control word an extended function program is also included in the conditional access data therefore the extended function program ciphered similarly is transmitted via the satellite as a plurality of packets inclusive of predetermined decoder id consequently only a decoder including the specific decoder id has an access right to these packets and is enabled to decipher the same whereby it is rendered possible merely for a user who paid a predetermined additional fee already to add the required extended function the cpu 6 transfers the extended function program which has been deciphered in the transport block 4 to the eeprom 9 and then stores the program therein fig2 shows a basic program stored in the rom 7 and extended function programs stored in the eeprom 9 more specifically the basic program stored in the rom 7 includes in its address a1 for example a branch step for the extended function program this branch step is so programmed that an address stored at each of e g entries t1 to t3 of the eeprom 9 is read and when the address is 0 it is regarded as no storage of any extended function.