Bird Technologies ACM Series-Manual - Manual (Page 17)

5
Chapter 2 Theory of Operation
Alarm Response
When an alarm is triggered, the Bird Antenna & Cable Monitor turns
on the alarm LED and activates a Form C dry contact relay.
The alarm relay defaults to fail/safe. That is, the alarm activates when
the relay is not energized or power is lost. However, the PCTool soft-
ware can configure the alarm to either energize or de-energize in
response to an alarm.
Alarm Reset
z Alarms can be reset locally with the reset switch.
z Alarms are reset when the reset pin on the Power/Alarm port
is activated by a TTL compatible logic low signal (0 to 0.8 Vdc).
z The PCTool can reset the unit through the RS-232 port by
sending a “Reset Alarm” command.
Alarm Latching
The alarm defaults to latching operation. In this mode, the alarm will
stay active until reset. In non-latching mode, the alarm will reset auto-
matically about forty seconds after the trigger 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:
z No alarm is activated if the VSWR is less than the maximum,
or if the VSWR alarm is disabled.
z If the VSWR is equal to or slightly greater than the maximum,
additional measurements are accumulated to determine a
trend. If reverse power is increasing, an alarm is triggered. If
the reverse power is stable, measurements continue until a
trend is established. An alarm will be triggered if the VSWR
exceeds the maximum for more than thirty seconds.
z If the VSWR is much greater than the maximum then an
alarm condition is triggered immediately.