User Manual DEV 1951
Copyright DEV Systemtechnik GmbH 2004-2017 37
E.g. in Individual switching mode the device switches a sensing switch module
(digital signal switch module) to the secondary input port if
on the primary input port, the RF level falls below the defined RF threshold
level (the digital signal quality becomes "Fail", respectively) and if
on the corresponding secondary input port, the RF level is above the
RF threshold level (the digital signal quality is "OK", respectively).
If neither Option 22 (main backup swap) nor Option 28 (automatic switch back) is
installed, there will be no automatic switching back to the primary input port.
In this case, the switching is to be done explicitly in Local Mode or in Remote Mode.
If Option 22 (main backup swap) is installed, the autonomous switching works in
both directions in the same manner as the switching from the primary to the
secondary input port (as described above).
This means that the device remains switched to the secondary input port unless on
the secondary input port the RF level falls below the RF threshold level (the digital
signal quality becomes "Fail", respectively) and if on the corresponding primary
input port the RF level is above the RF threshold level (the digital signal quality is
"OK", respectively).
If Option 28 (automatic switch back) is installed and activated (as described in
chapter 5.5.7.3.2), the switching back from the secondary to the primary input port
is initiated by the RF level rising above the RF threshold level again (the digital
signal quality becoming "OK" again, respectively) on the failing primary input port.
This switching back is supported by an offset which is an adjustable hysteresis
(0 dB, 1 dB, 3 dB, or 5 dB) for sensing switch modules, or which is an adjustable
delay (0…10 seconds) for digital signal switch modules.
For the autonomous switching capability has to be considered in addition, whether
Individual switching mode or Simultaneous switching mode is activated
(chapter 5.1.4) and whether (and which) input ports are disabled (chapters 5.5.4.1
& 5.9.4.3.9.2), since this has an influence on the switching behavior. Therefore, the
following scenarios are to be examined for the autonomous switching functionality:
Switching from the primary input port to the secondary input port in
Individual switching mode:
- If both input ports of a sensing switch module (or of a digital signal switch
module) are enabled, the switching is performed as described above.
I.e. the device switches only if on the primary input port the RF level falls
below the RF threshold level (the digital signal quality becomes "Fail", re-
spectively) and if on the corresponding secondary input port the RF level is
above the RF threshold level (the digital signal quality is "OK", respectively).
- If the primary input port of a sensing switch module (digital signal switch
module) is disabled, the RF level information (the digital signal quality infor-
mation, respectively) of the port is ignored as a trigger; i.e. the device does
not switch to the secondary input port.
- If the secondary input port of a sensing switch module (digital signal switch
module) is disabled, the RF level check (the digital signal quality check, re-
spectively) of this port is omitted. Thus, if the sensing switch module (digi-
tal signal switch module) is switched to the (enabled) primary input port
and if on the primary input port the RF level drops below the RF threshold
level (the digital signal quality becomes "Fail", respectively), the device un-
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