I have been reading and re-reading the Wikipedia reference to Code 128 and using the [FNC4] symbol together with the [SHIFT] symbol. What I am confused by is: When is the [SHIFT] symbol necessary for those symbols >= 224? I presume I would only need to use the [SHIFT] symbol if I were encoding Code 128A symbols and used the [FNC4] to reach those symbols. If I am already encoding Code 128B symbols, I should not need the [SHIFT] symbol. Is this safe to presume?

Further, if I am encoding Code 128A and I switch to the high order ASCII symbol subset using [FNC4][FNC4] sequence, if I use the [SHIFT] symbol, I should not need it again during this sequence. The Wikipedia article says that there is no defined way to encode the ASCII range 128-159. So, once I "turn on" the Code 128B extended set, it should remain on until I terminate this encodation with a subsequent [FNC4][FNC4] sequence (or the end of the barcode is reached, which is a moot observation).