r one million, with a calling rate of 1.25 calls per significant digital paging code formats used to date. second. Tone duration is 100mS and tone frequency relationship is a geometric progression. 45.7.3 POCSAG An outline of the POCSAG format is shown in Figure 45.3. A 45.7.2 Digital code formats transmission sequence starts with a series of alternate digits, 101010 as a preamble to awaken the paging receiver to obtain Bell Canada introduced its wide area digital paging system in 1970. synchronisation. This lasts for at least 576 bits which is equal to the Compared to sequential tone formats, digital formats can provide duration of one batch plus one codeword. A synchronisation code greater system address capacities, much greater battery economy word is then followed by eight frames, each two code words long. and thereby use smaller power cells, faster call rates, pager size Each pager is allocated an address in one of the eight frames and reduction by integration, additional functions such as storage of having gained synchronisation it need not turn fully on until that calls and messages in memory, multiple addresses and many other frame's time period, thereby saving battery power. features. Sweden inaugurated its national digital paging service If there is a message for a pager then it immediately follows the using a subcarrier on the national broadcast system in 1970 and address code word. It can be any number of consecutive code words Japan, already up to 600,000 on a tone system opened the NTT and may continue for more than one batch, but the synchronisation digital system in 1978. Meanwhile in North America the majority code word remains at the front of every batch. The message end is of systems supplied since 1973 were based on the Golay code always followed by the next address code word or an idle word. format. The receiver distinguishes address from message code words by In 1978 in the UK the British Post Office announced and agreed reading the first bit (F) which is a flag bit, equal to zero for an a c