Thanks, I understand the Mode S use.
In order to activate Mode S we also have to activate Modes A&C.
My real question is: Does it matter what Mode A we squawk while taxying?
It's actually a bit awkward to squawk 0000 until line up, because when you do line up you have:
(i) Stowed the Comms log on which the clnc is recorded, and
(ii) Forgotten the allocated squawk.......
Can we squawk the allocated A code while we taxy??????
Thanks