User Manual

“Halo” System: Communication Protocol 970-00002-000
EXI Wireless Systems, Confidential Page 14 of 33 July 27, 1999
4.1.4. Reset Command
The Reset command is issued by the Elevator when the door closes. The Elevator needs to know which
Tags are inside the Elevator and in order to force them to send their ID numbers again, it resets them all.
The Elevator will repeat this every time when the door opens and closes.
The Tags are in the sleep mode most of the time while in the field (to preserve power). They wake up once
every second to check if the field is still present. If they receive RESET command (0101) they will reset its
own internal flags which prevent them from responding to the BBB command, and become effectively
“unnamed”.
The Elevator sends RESET command 14 times in a row in order to catch all Tags which were in the sleep.
This RESET commands are spread across 1.4 seconds time interval, and because the Tag is waking up
every I second, all Tags present in the field should be reset.
Figure 4 shows the RESET command
4.2. Tag Initiated Communication (TIC alarm)
Besides being able to detect Tags presence within the “field of coverage”, the other important system’s
feature is to detect when the Tag is in the alarm mode. The conditions that will lead to this alarm mode are
different for different types of Tags. Actually all differences between Tags originate from one characteristic
– how is the alarm generated.
• P-Tag
The P-Tag is attached to the hand of the patient whose movement needs to be monitored and restricted (e.g.
newborn babies). Movement restriction is enforced by the TIF alarm but in order to be effective the P-Tag
must stay attached to the patient all the time. The removal of the P-Tag from the body will generate the TIC
alarm. The P-Tag is attached to the body with the elastic band and it is detecting body capacitance.
• A-Tag
The A-Tag is attached to the asset which movement is restricted (e.g. instrument that should not leave the
building). The movement restriction violation is monitored by the TIF alarms but it can be effective only
while the A-Tag is attached to the protected object. This is ensured by gluing the A-Tag to the asset and if it
is attempted to be removed, the plunger switch will close and generate the TIC alarm.
• D-Tag
The D-Tag is used by the user (e.g. nurse) as a “call for a help” when this person is in a distress. When the
D-Tag is pressed it will close the switch and generate the TIC alarm.
Figure 4 RESET command
‘1’
‘0’
WAKEUP
‘0’
‘0’
‘1’
‘1’
‘1’
‘1’
‘1’
‘0’
‘0’
‘1’
RESET