Wood and Douglas 1335, Operating Instructions Manual

Page: 16 / 91

16
1892 1335 - Orion Radio Modem Operating Instructions - v2.9 / Aug 2009
ALARMS AND ALERTS
v Alarms and Alerts only apply where there are telemetry inputs and outputs, and
therefore only to Modes
I and E.
An alarm is a state where an input has fulfilled a specified condition in terms of magnitude,
logic state, time etc. which requires some action such as sending a message. An alarm can
be raised, persist for a time, and then clear. There are two types in the Orion:
v Telemetry alarms
v Housekeeping alarms
Telemetry alarms relate to telemetry inputs. They can be defined in terms of input state and
history, and turned on and off.
Housekeeping alarms relate to communications problems and unit powering.
An alert is a non-telemetry output which may be asserted in response to an alarm being
raised, for a programmable period, typically to draw an operator’s attention to a problem.
An alarm message is normally sent when an alarm is first raised, and then again when it
clears. However, this behaviour can be suppressed by telling the unit that it may not initiate
transmissions.
If an Outstation sends an alarm message, it always expects an acknowledgement from the
Base. If it doesn’t get one, it may try again one or more times, and then if no
acknowledgement results, it will raise a comms failure alarm.
The table below summarises the parameters which define each alarm, and what conditions
lead to the alarm being raised or cleared.
Note: some AT commands have several parameters controlling related functions. Syntax and other details are
contained in the AT Parameter Reference on page 63.
Alarm Parameters Raise conditions Clear conditions
Digital input
(
ATS312 n where
n is input number
1-4)
State deemed to
be an alarm
Dwell time
On/off
Input transits to
nominated state and
stays there for the dwell
time Input returns to original
state and stays there for
the dwell time
Count input
(
ATS312 n where
n is input number
1-4)
Alarm Count
On/off
Nominated count is
reached Counter is reset
Analogue input
(
ATS302 n where
n is input number
1-4)
Polarity
(rising/falling)
Alarm level
Dwell time
On/off
Input rises/falls, reaching
or passing nominated
level and stays there for
the dwell time Input returns above or
below nominated level
and stays there for the
dwell time