The input tray switching program for this 'InputAliasName'
presented in a '.' separated list of prtInputIndex values.
For example, the string '1.4.3' indicates start with the
input tray represented by prtInputIndex 1, if it becomes
empty switch to prtInputIndex 4, when it becomes empty
switch to prtInputIndex 3, if it becomes empty then wait
for operator intervention.
An empty string shall indicate unspecified.