Bird Technologies ACMI - Manual (Page 15)

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Chapter 2 Theory of Operation
Alarm Response
When an alarm is triggered, the Bird Antenna & Cable Monitor turns on the
alarm LED and and de-asserts a TTL logic line (pulls low). In addition, depending
on configuration settings, one Form C dry contact relay changes state (i.e. acti-
vates or de-acitvates) as a result of the VSWR alarm activating. A second Form
C dry contact relay changes state as a result of either the low power or high
power alarms activating. Refer to the Power/Alarm Connector pins for proper
connection and Alarm configuration for set-up.
The LED activates the TTL logic line de-asserts as a result any of the three alarm
conditions (VSWR, low or high power).
If power to the unit is lost, both relays default to their de-energized condition.
The PCTool software can configure whether the relays energize or de-energize
during initialization or in response to an alarm when the unit is operating. Refer
to the section on Alarms for instructions on setting alarm response behavior.
Alarm Reset

Alarms can be reset locally with the reset switch.

Alarms are reset when the reset pin on the Power/Alarm port is acti-
vated by a TTL compatible logic low signal (0 to 0.8 VDC).

The PCTool can reset the unit through the Ethernet port by sending a
“Reset Alarm” command.

Reset events clear all three alarms (VSWR, High Power, Low Power)
and reset both relays.
Alarm Latching
The alarm defaults to latching operation. In this mode, the alarm will stay active
until reset. In non-latching mode, the VSWR alarm will reset automatically about
forty seconds after the trigger condition is corrected, power alarms will reset in
about one-and-half seconds after the power condition is corrected.
VSWR Alarm
The ACM continuously monitors forward and reflected power. From the power
measurements, the VSWR is calculated and compared to the allowed maximum
(default of 1.5 to 1). Based on the results of the comparison, possible actions
include: