13 October 2016

CIS Navy 50Bd/200 FSK (T600, BEE-36, CIS 36-50)

Sinchronous FSK 36-50Bd/200 system also known as CIS 36-59 and used by CIS Navy for their fleet broadcast. Transmissions start with an initial revs sequence transmitted at 36 Bd followed by traffic in 50 Bd mode. In case of more than one message, the initial 36 Bd reversals are not sent (Fig. 1).

Fig. 1
It's worth noting the presence of 2 x 70 bit repeated sequences in the preamble (likely the Message Indicator), also note the use of  a 4:3 ratio alphabet as well as the the End Of Transmission "000100" sequence which consists of at least 4 EOT characters (Fig. 2).

Fig. 3
Sometimes T600 is also used to forward flash messages in FSK/Morse mode as in Fig. 4 (transmitted by RDL HQ)

Fig. 4

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