As a driver, most signalling decisions are often irritating!
I recall, on another forum, an enquiry from someone who had just been accepted for training to become a signaller, they were uncertain as to what to wear for training, prior to uniform being issued.
The advice given by a driver was "bathrobe and carpet slippers, start as you mean to go on" another driver suggested "whatever you feel comfortable sleeping in"
As any driver will tell you, the whistle or horn is for waking up signallers. To be even handed, signallers refer to detonators as "drivers alarm clocks"