Alarms; Alarm Contact Types; Alarm Types - Videotec SM84A Manuel D'instructions

4.2 Alarms

The matrix provides a DB25 alarm connector, to which 8/16 (depending on the SM84A / SM164A model)
alarm contacts ("alarm input") can be attached, one for each of the input videos of the video device.
When an alarm is activated:
the keyboards able to display the alarm condition can activate a warning buzzer and may also show the
alarm status with a display message or a flashing LED (this type of operation is determined by the
characteristics and configuration of the individual keyboard).
each output that is enabled for recognition shows the video signal corresponding to the latest recognised
alarm in order of time; if an output is not enabled for recognition of the alarm condition, the alarm will not be
shown on the video
the alarm relay will be closed (auxiliary contact) and in some cases a warning buzzer is activated inside the
matrix, if this is allowed for by the alarm contact configuration
the text identifying the corresponding input is accompanied by the word "ALARM".
Alarm status will be stored internally and will be kept, even if there is a temporary interruption to the matrix
power supply. Warning! The alarms must be configured with special care, because a mistake in their settings
could cause faults in operation that are difficult to identify.
4.2.1 Alarm cont act types
Each individual alarm contact can be defined:
normally open (N.O.): the alarm condition is recognised when the alarm contact is short circuited to the
common alarm pin
normally closed (N.C.): the alarm condition is recognised when there is a break in the contact between the
alarm and common alarm pin
not used: the alarm contact is ignored.
Warning! Pins that are not connected to any alarm contact should be configured as NOT USED.
See the following example to understand how the alarm contacts function:
4.2.2 Alarm type s
The alarm signal can be considered CONTINUOUS or IMPULSIVE.
The difference lies in how the matrix behaves when the alarm signal ceases:
impulsive alarm: the matrix remains in alarm status, waiting for a reset (from the keyboard, external or timed)
continuous alarm: the matrix resets automatically and returns to normal operation without waiting for a reset.
Alarms normally open: the contacts are
disconnected from the common alarm pin.
When the contact is closed, alarm number 3 is
recognised.
Alarms normally closed: the contacts are
connected to the common alarm contact (pin
23-24-25). When the connection opened,
alarms 1 and 3 are recognised. This
configuration is also able to recognise as an
alarm a possible break in the cable
connecting the sensor and the matrix.
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