Videoswitch VT - Manual (Page 10)

VT Series 2 User Manual Page 10
Videoswitch
VT601c.doc
5. Alarm Handling
On the VT-14A, VT-18A and VT-28A, an alarm input is provided for each camera. These are for
connection to normally open contacts, typically provided by PIR or other types of detector. When a
contact closes, an alarm condition is triggered on that channel and preset may be called up on the
associated receiver if required (section 0).
5.1 Unlatched Alarm Mode
The unlatched alarm mode is suitable for unattended operation as in this mode, the transmitter
automatically reverts to normal operation when the alarms end. The audible bleeper is not sounded in
unlatched mode.
5.2 Latched Alarm Mode
The latched alarm mode provides the same facilities as the unlatched mode but requires that an operator
manually cancels the alarm conditions. While any latched or current alarms exist, an internal bleeper beeps
once per second until the SET key is pressed.
5.3 Alarm Processing
Multiple alarm handling is provided by the transmitter which ensures that any alarmed cameras are
displayed on Monitor A for a minimum time, and that multiple cameras with continuing alarm conditions
are displayed repeatedly in sequence. Alarm relay contacts provide the facility to control external
equipment in the event of an alarm.
5.3.1 Alarm Hold Time
When an alarm occurs, the associated camera is selected and displayed on Monitor A for the duration of
the Alarm Hold Time (section 6.5). If multiple alarms occur, each camera will displayed in turn, each one
for the duration Alarm Hold Time.
5.3.2 Alarm Dwell Time
When there is more than one alarm, and all alarmed cameras has been displayed once, the transmitter will
then sequence between the alarmed cameras, dwelling on each for the Multiple Alarm Dwell Time (section
6.6). This time may be different to the normal AUTO dwell time.
Sequencing will continue for as long as alarm conditions persist or, in latched mode, until the operator
presses a key to manually cancel the alarms.
When all alarms have cleared, if AUTO mode is selected, normal sequencing will re-start. If AUTO mode
is not selected, the last alarmed camera will be left on the display.
5.3.3 Alarm Relay Hold Time
When an alarm first occurs, the alarm relay in the transmitter will activate. When all alarms have cleared,
the relay will stay energised for the further duration of the Alarm Relay Hold Time (section 6.7) and then
turn off again.
The relay is typically used for an external warning device, to start and stop a VCR, or to switch a VCR
from time lapse mode to real time (3 hour) mode.