Rev. B
7-22
HMXMC001013
31-Mar-06
7.7
EXTERNAL ALARM INPUTS, CONTINUED
7.7.2 Front
Foyer
(PIR)
This example is of a PIR (passive-infra-red) detector connected to input (5) of the alarm
module located in slot (3) of subrack (12). It is a normally-closed input and will trigger if
the alarm circuit becomes open. Once the alarm is triggered it will LATCH. This alarm
must be cleared by an operator. It will not clear automatically. When triggered this alarm
will execute its START MACRO sequence. VCR (1) will select camera (47) and then go
into record. When the alarm is cleared, the FINISH MACRO is executed. The finish
macro sequence first tests if there are any more alarms still active on the video system.
If there are no more active alarms then VCR (1) is stopped.
CAUTION:
This alarm is also defaulted as DISABLED, so
it will not function until it is enabled. This can be done
from the system menu or automatically by a timed-
macro-event.
7.7.3
Door Contact Alarm
When controlling doors and other types of access management it is necessary for the
video system to watch the status of door contacts. This alarm definition simply attaches
an alarm identity to the door contact connected to input (6) of the alarm module located
in slot (3) of subrack (12). When the door opens (contact opens) the alarm is triggered.
As this alarm is assigned to display group (0) it does not display any message. It is not
added to the system alarm stack. It does, however, execute its START MACRO although
in our case there is nothing defined. The status of this alarm definition is set to ACTIVE.
Other alarm or macro events can test this door alarm to decide what action they can do
(e.g. door interlock management). When the door closes this alarm will clear itself. So
this alarm follows the true state of the door contact (invisibly). As this alarm is also
LINKED into the network, it will broadcast any change-of-state to all other video system
nodes.
7.7.4 High-Level
Alarm
High-level alarms are used to signal the video system of external alarm events gathered
by a separate alarm management system. These alarm states are communicated via an
RS-232 data connection between the two systems. The alarm management system
simulates a MAX-PROTOCOL command indicating the state change.
In the case of this example the command would represent, input (1) of slot (1) in subrack
identity (999). As this alarm is defined as DIRECT-MODE the alarm management system
would be responsible for clearing the alarm state. It is the responsibility of the video
system to present the correct cameras (and control VCRs etc.), not manage the alarm
itself.
When the alarm management system ACTIVATES this alarm in the video system, the
assigned START-MACRO sequence would be executed. In this case, loading variable
(01) with value (4), then running macro line (200) in the system macro library table. As
this alarm is assigned to alarm-display-group (2), only monitors allocated this alarm
display group will display the flashing alarm text message.
