[ANNEX VIII U.K. SPECIALISED OPERATIONS [PART-SPO]
SUBPART D INSTRUMENTS, DATA AND EQUIPMENT U.K.
SECTION 1 U.K. Aeroplanes
SPO.IDE.A.210 Headset U.K.
(b) Aeroplanes operated under IFR or at night shall be equipped with a transmit button on the manual pitch and roll control for each required flight crew member. ]U.K.