Description: Assigns one of N allowed standby frequency pairs to the radio 
transmitter and reciever as described in zhoneRadio-TC.mib.

5.7Ghz family (sysObjId) systems:
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Selection of one of N possible frequency pairs for the 
standby radio transmitter reciever.  

The Standby channel is the channel automatically switched to
in the event of failure of the current active channel, for example,
due to radio inteference. Automatic Switching must be enabled for
the standby channel to be switched to by setting wtnAutoChannelSwitchEnable
to true.

If the standby channel is assigned a value of zero (0), the automatic
switch to standby feature is effectively disabled, regardless of
the value of wtnAutoChannelSwitchEnable.

The channel is switched at the near end, and if possible, also at
the far end, towards minimizing link down time.  


Allowed range of allowed values (see zhoneRadio-TC.mib ): 0 - 17

This value will read back the current standby channel.

Operation - 
If a switch-to-standby channel event occurs, the active channel
number and the standby channel number swap values.  For example, 

before a radio failure:  active channel = 1, 
                         standby channel = 7, and 
                         automatic channel switching is enabled.

After a radio failure on channel 1:
                         active channel = 7,
                         standby channel = 1, and
                         automatic channel switching is enabled.

If both channels fail to operate, the system will bounce back
and forth between the active and standby channels until the radio
link is re-established.


23Ghz family sysObjId systems: 
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This variable is not used and so should not be presented to user.
Use direct frequency assignments instead.   
See wtnStandbyTransmitFrequency.