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PAN's

From: <>
Date: Fri, 1 Dec 2000 12:55:02 +0100 (CET)

Brandon Macmillan writes:

 > IIRC he was saying that if two people with wearables and PAN's were 
 > to shake hands they could transfer data across the link, COOL tech if 
 > you ask me

The body is electrically conducting, being a bag of
electrolytes. Shaking hands temporarily creates a connection of
varying resistivity (it is highly variable on how you shake hands and
the amount of salt/sweat on it). Think of it as two aquaria with salt
water and electrodes, connected by a salt bridge. Now think how you'd
set up an RS232 connection over this.

The problems I see is that you need some reference potential (you have
only one wire, your ground is probably floating), and a good
connection to the skin (or a higher voltage, as well as protection
against electrostatics (you've certainly zapped people with
electricity when giving hands, electronics doesn't like this either).

It can be done and has been done, though I don't quite see the point
apart from a certain neat symbolism (handshaking protocol, eh?). Me, I
wonder what's wrong with (boosted) IrDA or Bluetooth. Building a laser
diode into your HMD (just for show, of course, you'd want to use a
digitally controlled NIR LED cluster lamp -- also handy for
illumination) is the height of Borg fashion (good for optical marker
if you have a CCD or MCP night vision hookup).

 > I was meaning to start a whole different thread on this but here goes 
 > anyways: My latest greatest and craziest idea is this, do you 
 > remember a while back a guy who embedded a microchip encapsulated 
 > in glass into his leg, it did relatively nothing, transmitted back a 

You're talking about a transponder. Go to the nearest pet shelter (or
a large stable), and let the application of technology be demonstrated
to you. Before, go look up "transponder" on Google.

 > bar code when hit with a certain RF frequency. what I want to do is 

Nope, it's a little encapsulated semiconductor radio emitting a code,
which is energized by an external electromagnetic coil (built into the
reader). Because field decays so sharply and the thing is emplanted
into a strongly RF-shielding environment (body), it only works at
close proximity. Some BMW cars use a transponder in a car key,
energized by a coil around the ignition lock. This way the car
remembers individual user's preferences, and restores the saved state
associated with a given key when you start it.

 > encapsulate in glass and embed in my lip and ear cartilage a 
 > microphone and a speaker based on vibrations like that cell phone 
 > where you stick your finger in your ear. and then have them talk to 
 > my wearable via a PAN to do TTS and STT with Emacspeak. powering 
 > the devices is still to be worked out but....
 > 
 > Comments all??

Only meta level: in the real world, you first look for what is
sensible, and then try to solve it in a straightforward way (because
things are difficult enough already).

Designing, building and powering working legal emplantable stuff is
highly hairy. If you omit the "legal" requirements, things become much
easier (and cheaper). 

Then, there is this little question of "what on earth for?".

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