>    ~ the guard has to 'check-in' at various check points (there are four
of
>them, I was thinking about using long range remotes with a receiver in the
>guard room. The guard has to check-in, in a sequence, so that he cannot
>stand in one place and 'press the button' four times.)
>    ~ Once the guard has completed his patrol, he has to 'reset' the system
>by pressing a button inside the guard room.


How about each check in station and the ID unit the guard carries each have
a serial number device such as a Dallas i-button in it along with an RTC. To
check in the guard holds his ID device against the check in point device at
which point they exchange serial numbers and log the time of exchange. This
would be done through an RFID type technique.

When the guard gets back to the guard room he holds his ID device against
the guard room check in point, and serial numbers are exchanged again. This
does the 'reset' of the system. Once this is done, the guard room point then
downloads the log from the guards ID device, thereby providing an auditable
log of times and check ins. There is also some sort of connection from the
check in points to signify that a check in was made, but not carrying the
serial number info, although it would need to signal that it was a valid
serial number. These contact times are checked against the downloaded log to
see that they were done in correct order.

Perhaps too complicated for what you are trying to do?

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