X-Message-Number: 8278
Date: Tue, 3 Jun 1997 20:00:45 +0200 (MET DST)
From: Eugene Leitl <>
Subject: automatic death alert

Recently, Kennita Watson made a number of quite good points
about an automatic personal alert gadget for cryonics purposes.
I'd like to make a few short comments on them.

1) Kennita, you should contact Hara Ra ()
directly, he's the focus for those attempting to build such a

2) Those pulse watches I inspected are no good. Believe me,
nobody would wear a breast belt for longer periods of time
(that is, unless he has a faible for rubber SM). Being designed
for joggers, the conductive rubber assumes constant presence of
a sweat film for electrolyte, which has to be faked with
electrolyte gel, yuck. And even then, they drop signal all the

3) Electrocardiogramme alone is no good. Simultanous evaluation
of several _noisy_ biosignatures is required, one needs a RC
delay signal processing as minimum, and a trend evaluation for
sure. Hara Ra said a M68HC11 embedded controller would suffice,
I concur. TI's low power DSP/embedded hybrides might be more
adequate, though.

Best thing would seem to design the gadget something akin to a
bulky wristwatch, very like a G-Shock. Multichannel biotelemetry
goes to an immobile station hooked to the phone line, which then
dials the CSP (Alcor, whatever), and yells for help. Movement,
temperature, and photoplethysmography (cardiac-frequency
modulation of tissue-backscattered NIR light) seem to suffice.
If the gadget thinks you're ready for the dewar, it beeps first.
If you don't reset the countdown, it only then dials out (this
to prevent blind alarms). Power demands are pretty alarming,
even for a burst mode for both wrist sensors, and the RF sender
(ultrasonics is no good). Don't expect more than 48 h life time
--so one needs two gadgets, and a recharging station.

If one'd like permanent go-anywhere biotracking with (possibly
differential) GPS and a cellular modem (but, unless you are on
an outdoors hike, people are likely to notice if a guy drops
down dead), one could use a belt-worn system picking up
biotelemetry from the wristwatch mounted sensors, which
drastically reduces battery demand. I guess a bulky Li-Ion could
live for a month, or so, then.

4) Vanilla GPS is no good. Garmin drops signal in the city much
too frequently. Sirf's (company's California-located) GPS
chipset sells for just 49$ in OEM quantities, and is said to
reacquire a fix in few 10 ms if a transient outage appears. It's
firmware is said to be optimized for urban and foliage areas,
and yes, it can do DGPS. I have no experience with their system
though. Might well be marketing hype. Please notice the antenna
must be always horizontally mounted, and does not tolerate any
noticeable shading -- it must be located on a shoulder
(concealed by clothing), or worn on the top of the head/hat
(this is no joke). Caution, a GPS is a power-thirsty device,
it's powerful DSP and microwave receiver part cum active antenna
considered. Since one obviously needs a fix history, this spells
a big battery, even sophisticated power management considered.

Unless you belong to these very, very few who walk around with a
wearable, and a head-up (those guys get a very solid platform
infrastructure basically for free), you've got to accept a
noticeable belt-worn box, and a minimum of wiring (for the GPS

5) A cellular phone which is on can be located to a few 100 m,
since it talks with cell-local machinery. Such services are
available in Germany, albeit solely for special police forces
(perfect surveilance: who has been talking to whom, when, where,
and what did he say). Things might be different in the U.S.,
contact you cellular provider, possibly one might work out a
possible solution.

6) Once you've got some 10 customers, things are getting hairy.
Idle cyclic calls, call time slots, multiple lines,
authentication, resistance to malicious jamming, no-fail and
fail-safe etc. issues come up, so questions of the
appropriate protocol and centrale complexity (UPS,
decentralization) can no longer be ignored.

Sure, nothing can be 100% failure-proof, but a mission critical
has got certain minimum standards.

I sure forgot about a 1 k things, but this gotta suffice now.


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