System Products 171
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S_ACT (Secondary Active Contact Output) / P_ACT (Primary Active Contact Output):
The S_ACT and P_ACT contact outputs will inform the external device whether the primary or
secondary is active.
For example, when the RU status switches to the primary, the P_ACT is close contact,
and S_ACT is open contact.
S_WD (Secondary Watching Dog Contact Inputs) / P_WD (Primary Watching Dog Contact
Inputs):
Connect the P_WD and S_WD inputs to the the Bypass Mode output on IDA8 processor. When
IDA8 enters the bypass mode, the Bypass Mode output will inform the RU units, and the RU unit
will determine whether to activate the primary IDA8 or the secondary IDA8 processor by the
monitored P_WD and S_WD contact inputs.
The basic philosophy is that the master RU unit monitors the P_WD and S_WD inputs coming
from the primary and secondary IDA8 processors and decide which one can be active, and also
passes the decision to next RU units through EXP_OUT terminal. See the table as below.
For example, when RU detects P_WD and S_WD contact are closed, it switches to the
primary.
If the RU unit is set as the slave RU unit, it monitors the S_WD which connects to the
master RU unit, resulting in setting the primary or secondary IDA8 processors to be active.
Master/Slave Switch:
A DIP switch to set RU-PDC be master or slave. The difference between master and slave
please refer to item "(S_WD)Secondary Watching Dog".
3.3.3 RU-PDC
RU-PDC device is a device supplied with full-redundancy for audio processor. It is in charge of
switching primary and secondary audio processor to active one of them. If primary audio processor is
active, all signal of peripherals shall be directed to the primary audio processor. RU-PDC device is
also capable to monitor the status of audio processor. If primary audio processor breaks down, RU-
PDC device will detect automatically and switch to secondary audio processor.
3.3.3.1 Front Panel
Secondary Active Indicator:
This LED lights up if active system is primary audio processor.