D2.6 Circuit Operation M8SL2-00-002-812
© Copyright Tait Electronics Limited August 2004. All rights reserved.
2.3.1 Alarm Triggers
The alarms are triggered according to their type.
Table 2.1 Alarm Summary Table
External Closure Alarm (Auxiliary Input Alarms)
The 8 bit input latch (IC202) is sampled every 50ms. If two successive samples are the
same value then the state of the closure alarms is tested (This has the effect of debounc-
ing the alarm inputs). If any alarm is low then those alarms are latched.
RF Power Alarm
The forward and reverse power alarms are only tested when the T803 is keying the
transmitter. The alarms must be active (low) for two seconds before they are latched.
The two seconds sampling period allows for settling time inherent in some older T800
PA designs. Note that if a Transmitter fitted with a T1500-52-0000 PCB is being used,
rack backplane links LK1 and LK2 must be fitted at power up.
Low Battery Alarm
The 13.8V supply line voltage is measured by the A/D converter (IC208) every 50ms. If
the voltage is below the programmed alarm threshold (±0.05V) for more than 25 sec-
onds of a 30 second sampling period, the alarm is latched. The long sampling period
allows for load fluctuation effects on the supply.
Programmable low voltage threshold is only available in T803 firmware version 2.11 or
later. Prior to this, the threshold was fixed at 10.7V ±0.05V.
Line Fail Alarm
If no keying from line occurs within the period programmed by the user from
PGM800Win, the microprocessor latches this alarm, saves the mode status and puts the
T803 into repeater mode. Note that programming zero as the line fail time disables this
alarm.
Priority Alarm Type Trigger Type
Re-triggerable
when latched
LED
colour
1
Auxiliary Input 0
to Input 3
External closure. Sampled
every 50ms
Yes Green
2 Reverse Power Sampled every 50ms
while the T803 is keying
the transmitter. Incoro-
rates a 2s settling time.
No Red
3 Forward Power
4Low Battery
Voltage must be belo w
the programmed thresh-
old for 25s of a 30s period.
No Red
5Line Fail
Programmable non-activ-
ity time period
No Red
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