You actually have three side imaging frequencies, but the lowest, 262 kHz, is not mentioned in the manual. The frequencies are set by the selection made in the Transducer Select menu. Obviously, your unit must be set to Sidescan which means the unit operates at 455 and 262 kHz. This setting is used with the old XHS 9 SI 160T transducer. If you have the newer XHS 9 HDSI 180T transducer the unit should be set to Hi-Def sidescan in the Transducer Select menu. The instructions on how to set the units for different transducers has always been obscure, to say the least.
Rickard