Dave,
WRU is the ASCII key or code to trigger a DE "Here Is". Used almost exclusively on TWX machines.
Baudot is "FIGS D" character to do the same on Telex. You should disable your AB drum from being tripped by DE as when the machine is garbling it can trip your AB and guarantee the next 20 characters will be garble.
Both ASCII and Baudot have mechanical blocks so you dont trip your AB from the kybd tape.
More on this tomorrow when its a bit earlier.
73,
Wayne