🚀 go-pugleaf

In article <205@nbc1.UUCP> abs@nbc1.UUCP (Andrew Siegel) writes:
>I've been wondering for a while about those card-keyed door locks
>that you find in newer hotels.

I discovered answers to this in my last trip to the 'apple',
since my electronic door lock stopped working.  I asked these
same questions of the repairman.  Enjoy.

>                                  I have three questions:
>	1) How are they powered?  (I can find no evidence of wires
>	   running to the door itself.)
Batteries.  Nice heavy duty commercial ones at that.

>	
>	2) What is the means by which they are reprogrammed?  Is
>	   it done using RF?  Carrier current?  Microwaves?
They aren't really "reprogrammed" per se.  Each one is
pre-programmed with sequence of valid card key numbers.  The
machine that punches the keys also knows of the sequence, and
keeps track of the number in the sequence that any given lock
is on.  It generates a key in sequence for every new guest of
that room/lock.

When a key is inserted in the door, the lock checks
1) whether the number is the number of the current key, in
which case it opens the door, or
2) if not 1), whether it is the next number in the sequence,
in which case it increments it's pointer to the series, and
calls this number the "current" number.  And so on, in
sequence.  I don't know if all locks have the same sequence,
or what that sequence is.  I would imagine they all do, and
that the sequence is not ascending numeric.

>	
>	3) If they are battery powered, what kind of batteries
>	   are used, how often must they be replaced, and how
>	   does one open the lock to replace the batteries?

See above for batteries.
When the battery dies!, a manual override is available with a
special key, which allows the door to be opened.  After being
opened, it is a simple matter to remove the back side, add
new battery, and put things together again.  Actually fairly secure.
The repairman said a battery lasts about 6 months.  Note that
one of two things must be happening.  The sequence, and current
pointer must be in non-volatile memory, because our key worked when
the batteries were added.  Alternatively, the repairman may
have been graceful enough to know that he should use our key
_first_ after repair, as possibly only the sequence is in
NVROM and the pointer is set by using the first key number
encountered after fresh power up.

>-- 
>Andrew Siegel, N2CN		NBC Computer Imaging, New York, NY
>philabs!nbc1!abs		(212)664-5776

--------

Here I am, brain the size of a planet, and I'm being made to
write applications programs, and nobody cares about the pain I
have in the diodes up and down my arm.

Jay Batson
siesmo!{nbires,hao}!isis!jay