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Abstract

A pager decoding system which is suitable for use with signal formats, such as POCSAG, in which code words are sent in batches, each batch containing a synchronization code word and (n-1) address/message code words, n being the number of code words in a batch, each code word comprising m bits. The pager is able to detect or regain synchronization code word when the carrier signal is lost due to fading. When synchronization is lost input data received by the pager is combed through by switching-on the pager for a duration of m bits at intervals corresponding to (n+1) code words. The data received is stored in a shift register having m stages and in which a synchronization code word can be assembled within two batch periods. Once the synchronization code word has been detected the pager can be switched to a normal data receive mode. In another fade recovery mode the (m-1)th, mth, and (m+1)th bit positions every nth code word are searched to see if a preamble or synchronization code word is present. If none is detected after a predetermined number of batches has been searched then the pager assumes the loss of synchronization mode described above.

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First Claim