In BETA if opener makes a jump rebid in a new short suit - this is conventional (not following a 1
opening): It informs partner:
a) My first bid suit is my only suit (that's a single suited hand)
b) I'm (15)16+ in HCP and this is FORCING. Shows interest in reaching game
c) My rebid shows usually two top honours and precisely 2-3 cards
(occasionally can be bid on a singleton Ace ONLY with a 6331
distribution).