RE: URGENT : Ideas Wanted

[nigel@xxxxxxx]

On 08-Jan-2001 Doogie Brodie wrote:
> physically walk to the machine and press your finger to it. Does
> anyone know what sort of range these devices could have (eg, whats
> the current range of an ibutton?)

The embedded ones are limited by power- they need a sufficiently
strong field from the reader to power them, and produce enough RF
back to get a reliable signal.  In practice, the dog ones are about
100mm with a standard reader, obviously you could have a more
powerful transmitter, and more sensitive antenna and tweak it a bit
more, certainly enough to cover a doorway.

They're cheap too, well under a tenner in 10s or more (though you can
expect to pay more to have it 'installed'!!)

They are usually implanted in the shoulder or neck, which saves too
much faffing about with the scanner.  A paper a few months back in
the Veterinary Record (light bedtime reading) gave quite a lot of
detail about migration round the (animal) body from various locations,
IIRC the shoulder muscle turned out to be the best, but I can't
remember the details, it's not unknown for them to move a couple of
inches.

And the needle is about the size of a biro :-)

ibuttons aren't wireless, maximum cable length is spec'ed at about
200m or so with cat5.

Nigel (not had a radio tag installed in me, don't intend to, before
you ask!)