other keys).
Logging mode on/off: when on will display the preamble
(identification number) of all messages received. When off ignores
completely messages/stations not programmed.
Paper feed key.
Alarm on/off key: an alarm will always sound when category 'D'
(Search and Rescue - SAR) messages are received, even in the
alarm-off position. Alarm-on will sound the alarm when other
messages (particularly category A and B) are received. The alarm
will also sound when the paper has run out.
AIarm stop button (to silence the alarm - may be combined with
another function).- Receiver monitor: allows you to listen to the received signal (as a
check on reception - not because you are expected to understand
the telex-type noise!).
Self test facility: this allows a complete check on all parts of the
receiver system, when you suspect you may have a problem (e.g.
not receiving messages from your programmed station at the
published times).
Station/message selection
Having found your nearest station from ALRS Vo!. 5, you also
have to tell your equipment what types of message you require. When
the receiver is fitted for the first time it will normally be programmed to
receive every type of message from all station ID letters, so you will be
rejecting stations/messages rather than programming-in.
Ail messages start with an identification sequence consisting of
two letters and two figures, e.g. GAOl; G B22 - where the first letter is
the station ID and the second letter is the subject indicator (full list shown
in ALRS Vol. 5 NAVTEX section). Some message categories are:
A Navigation Warnings. This category will be fixed into your receiver.
You will not be able to reject message type A.
B Meteorological Warnings. Gale/storm warnings - also fixed and
cannot be rejected.
D SAR Messages. Mainly initial and final messages regarding a SAR
operation in the area - cannot be rejected by the receiver.
E Meteorological Forecasts - the (usually twice daily) weather forecast.
Probably the most-wanted information after A and B but is not fixed
into your equipment. You must ensure that it is programmed-in.
L Navigation Warnings (additional to letter A). This category should
184 THE NAUTICAL INSTITUTE