| 摘要 |
In each receiver (40) at least one datecode is stored which defines a subscription period during which the receiver is entitled to display received messages. For each message (200) to be transmitted, a datecode which defines a particular subscription date to be associated with the message is generated, the datecode defined by a predetermined number of bits. The datecode is compressed into a compressed datecode (220) based on the datecode, the compressed datecode being less in number of bits than the predetermined number of bits of the corresponding datecode. A modified checksum word (230) for the message is generated based on the plurality of bits which represent the message (200) and the predetermined number of bits which represent the datecode that corresponds to the compressed datecode (220). The modified checksum word (230) is associated with the message and the compressed datecode (220) for transmission.
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