  It is generally accepted that no `faster than light signalling' (FTLS) using
two entangled spin 1/2 particles is possible because of indeterminism in a
quantum measurement and linearity of standard quantum mechanics. We show how in
principle one bit of information could be transmitted using local measurements
and a global unitary transformation of the state of two entangled spatially
separated spin 1/2 particles. Assuming that the postulate of a state collapse
due to measurement is valid, the no FTLS condition is saved if we do not have
physical access to the required global unitary transformation. This means that
the no FTLS condition is also present on the operational level, namely as
imposing a physical restriction on the possible realizable unitary
transformations, in this case of two entangled but spatially separated spin
1/2.
