Provided is a vehicle seat reclining apparatus comprising: a first bracket, a second bracket, a pole, a cam, a locking urging member, a hinge pin, a fitting hole, a release lever, and a supporting urging member. The maximum value is applied to a a master curve corrected from the results of a test of simulating an actual machine and a test piece of actual machine size, taking account of internal damage of the machine. The isolated narrow band signal is then processed to detect repeating features of the narrow band signal. The transmitting and receiving is then controlled so that the transmit periods do not overlap with the ranging periods.