Processing Priority; Tampers And The Bus - Eaton i-on series Engineering Manual

The System Bus
Note that you cannot allocate zones to both an expander AND a KEY-KPZ01. This means,
for example, that allocating zones on the i-on30EX to a KEY-KPZ01 will make eight
zones unavailable to expanders at the top of the zone number range.

Processing Priority

When several detectors are activated at the same time, the control unit always processes
HUA and Normal Alarm detectors first, followed by Fire, and then all other alarm types.
The control unit always processes alarms before Alerts.

Tampers and the Bus

Every device that can be attached to the bus has its own anti-tamper switch. When this
switch is triggered the device sends a message down the bus to the control unit, which
then starts the appropriate alarms, shows a tamper alert on the keypad and communicates
a tamper message to the ARC.
If a bus device is disabled, and cannot send any messages on the bus then the control unit
marks it as "missing". (A bus device might be disabled by physical damage, loss of power,
or by a cut bus cable.) The control unit starts a tamper alarm and displays an alert at the
keypad, for example "P1:Missing R1-03" for an expander or "P1:Missing K1-52" for a
keypad. In a Grade 3 system the control unit will also communicate a missing bus device
to the ARC as a tamper.
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i-on Range