You can quite safely use personal radios in the back, as many troops do. You will notice that some of the team are wearing flying helmets so could plug into the intercom system. The problem comes with tangled up leads and live mics so most times (certainly on the Merlin) the IRT Docs and medics need to work 'unattached'. They also need both hands free so often shouting is the simplest and easiest way to operate.
