PURPOSE: To eliminate the need for an expensive down-converter by receiving number information of an SCPC wave during transmission from an SCPC terminal station device and obtaining a mean power of each SCPC wave through the operation from the said information, the information of the level difference of two sets of SCPC waves and total power such as a transmitter output.

CONSTITUTION: A total power Ptotal in a diode detector 21 is expressed as Ptotal=PA×NA+PB×NB, where PA is a mean power of the SCPC wave of a group A, PB is a mean power of the SCPC wave of a group B, NA is a number of the SCPC wave of the group A during transmission at present, NB is a number of the SCPC waves of the group B during the transmission at present, and (x) is the ratio of the PA and the PB. The mean power of the SCPC wave of the group B is obtained from the Ptotal, NA, NB and the X, and further by the PA, PB and the X. In order to match the timing accurately, both the signals are established by proper first-order filters 19, 20.