
When \onoff\ is used with \sww\ (\commandVerbose{SWWOBBLER}),
the position offsets 
must be set to very specific values in \truehorizon\, 
depending on the parameters of \command{SWWOBBLER}.
This is achieved by using the special option \option{/SWWOBBLER}
of the \commandVerbose{ONOFF}. 

Subscans are then taken alternating between 2 positions
in such a way that:
({\it a})  in some subscans (one position of the antenna) 
     the source is in the first of the two Wobbler phases,
({\it b}) in the other subscans (the other position of the antenna)
     the source is in the second of the two Wobbler phases.
During the data processing, the source signal is computed
as a double difference: 
1st the difference of the 2 Wobbler phases; 
2nd the difference between \onoff\ subscans ({\it a}) and ({\it b}).

This form of \onoff\ is also called ``Wobbler-Onoff''
or sometimes simply ``Wobbler Switching''.

