A slave apparatus control portion refers to a priority channel table stored in a use priority channel memory at the time of establishing communications with a host apparatus. The radio channel having the highest priority is allocated as the initial channel, and a connection request signal is transmitted from a communicating portion to the host apparatus in the frequency band of the initial channel. When the initial channel interferes with the radio channels used by other slave apparatuses or the frequency bands used by PCs, the radio channel overlapping those frequency bands is avoided, and the radio channel of the frequency band that is the second highest priority is selected.