Allows sub-rcvr to be on different band than Main receiver.
This is a Power On function mod.
Start with radio turned off.
Hold down buttons SUB, M/S, RX/SUB while turning on the power ON. Now you can listen to 15M on sub-rcvr with Main rcvr on 20M. or any other band or visa-versa. Both receivers will be in the same mode USB, LSB, CW etc.