An extension subordinate machine system enabling high-accuracy correction of the cable loss by adjusting the gain by using the pilot signal and further enabling high-accuracy correction of the loss caused by distribution by a distributor even when a relay device adaptor is connected to the extension subordinate machine through the distributor. With this system, a main machine control section (201) outputs a pilot signal generated by a pilot signal generating section (203) when a switching section (205) sets a measurement mode. A pilot detecting section (215) detects the reception level. A control section (216) detects the pilot signal and sets the attenuation factor according to the reception level of the detected pilot signal. A variable attenuator (206) attenuates the up-link signal and the down-link signal at the set attenuation factor to adjust the gain.