GB> Copied from 12952.4 kc tonite.

Jeffrey Herman (WH6U) jeffreyh at HAWAII.EDU
Tue Jan 26 22:19:36 EST 1999

Great discussion going on (on the various lists above). One very
important thing to remember (which will make monitoring 500 kc oh so
easy for us) is that ITU format ships must follow for sending a distress
message includes the wonderful but simple Auto Alarm Signal: During
an international radio conference earlier in the century (which one? I've
never been able to pin down which conference), a method for alerting
off-duty radio officers (ROs) that a distress message was occuring
on 500 kc was created. The RO aboard the distressed vessel would send
(either by hand or by a keying device) twelve 4-second dashes, with
a one-second space between each dash (on many a shipboard clock
you'll see twelve 4-second red arcs running the full perimeter of the
clock's face to aid the RO). Aboard all other ships was an Auto Alarm
Receiver which contained a host of timers and relays - after receiving
just four correctly timed dashes, relays in the AA receiver would
clamp shut, sounding bells and lights in the radio room, in the RO's
stateroom, and in the bridge. Thus, even with the RO off duty, he'd
be notified that he was within radio range of a distress.

(Those who've heard an Auto Alarm signal have felt the helpless and scary
feeling waiting for those 12 very long dashes to cease, knowing that
men may be perishing in an icy sea...)

Thus, for those who'd like to keep a round the clock 500 kc watch,
you might consider building a timing device to clock the 4-second
dashes. (I've got a schematic of a Mackey Marine AA receiver from
the late 30s just in case any of the GB or BA folks are up to the

73 all, Jeff WH6U (ex KH6OO)

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