From: John De Armond
Subject: Re: Access control for doors to shower
Date: Fri, 06 Apr 2001 14:59:00 -0400
> Wow, yes, very pricy. Any other ideas?
What are you trying to control? That would dictate what you use.
BTW, those door locks with the 4 or 5 pushbuttons that must be
pushed in a specified combination are trivially easy to "pick".
After the mechanism gets a little (few days) use, it is easy for a
person who knows what to feel for to feel the combination and open
the door. A lot of computer rooms use these locks and when I was on
a client's site, I could usually give myself access to the room with
just a couple of minutes of manipulating the buttons.
Probably the cheapest low security solution will be an electronic
keypad lock and either an electric door striker or an
electromagnetic latch. Look on the net for home automation
dealers. Most alarm companies sell these also.
Another possibility is the use of the Dallas Semi Ibutton. The
Ibutton is a cryptographically secure electronic serial number
device that looks like a watch battery. Each individual device has
a globally unique serial number. It is read by simply touching the
device to a touch station for a fraction of a second. For access
control, the lock controller is simply programmed with the
authorized serial numbers. The Ibutton is very cheap - under $3
from Dallas, a couple more from resellers so if it gets lost, no big
deal, particularly if the customer pays a deposit. For access
control, an Ibutton is issued to the customer when he checks in and
a deposit kept. The button is available embedded in a keyfob, a
ring that can be worn and a pendant, among others.
The nice thing about the Ibutton system is that multi-tiered access
can be implemented very easily. Say, you wanted to give customers
access to the showers but charged extra for the game room. Simple
to program the system so the customer's Ibutton is only authorized
on the bathhouse lock but not the game room.
The Ibutton, along with all the other devices in the family
communicate using Dallas's 1-Wire (TM) technology. That is, the
minimal configuration to the button reader, the lock controllers,
etc, is a single wire plus ground. For long distances, Dallas
recommends using a 3rd wire for power. Ordinary Cat 1 or 3 phone
wire works wonderfully for the 1-wire network.
Ibuttons can also be used for inventory control. If you rent
bicycles, canoes, etc, simply permanently attach an Ibutton to each
capital item. Then when it is rented (or loaned) to the customer,
the Ibutton is read by briefly touching it with a handheld touch
reader. The inventory management software then associates this
serial number with the customer account. They're waterproof so they
even work on things that go underwater, stuff like SCUBA tanks.
Ibuttons are also available with an internal clock. These can be
used for keeping time for time-based rentals. Since the actual time
is kept in the device attached to the asset, no need for a computer
network. The rental time is simply delivered to whatever reader
(even a handheld unit) is used during check in.
Maytag is using this system to manage their semi trailer leased
fleet. Very slick system.
If you go to Dallas's (http://www.dallasemi.com, I think), you can
find a page that links to many of their VARs. The VARs take the
Ibutton devices and incorporate them into end-user devices like
access control systems. If you don't want to build the system
yourself, this is the way to go.
Whatever you do, you must consider emergency access. The locks
should fail open on power failure (the electromagnetic door latch
does this), the fire alarm should open the locks and there should be
an emergency access switch, usually a "break glass" or pull
station. There is probably a fire code that addresses this, though
it is just good old common sense.