a reference clock generating step for generating a reference clock;

a test signal generating step for generating a test signal based on said reference clock;

a transmitting step for transmitting, with a transmitting unit, said test signal generated in said test signal generating step;

a receiving step for receiving, with a receiving unit, said test signal which said transmitting unit has transmitted in said transmitting step;

an anticipated value generating step for generating, based on said reference clock, an anticipated value for said test signal which said receiving unit is to receive in said receiving step; a delay step for delaying said test signal which said receiving unit has received in said receiving step, as to said reference clock;

a comparing step for comparing said test signal delayed in said delay step with said anticipated value generated in said anticipated value generating step, and outputting comparison results indicating matching or not matching;

a comparison result storing step for storing said comparison results in said comparing step in a manner correlated with the delay time by which said test signal was delayed in said delay step;

a repetition step for repeatedly performing said delay step, said comparing step, and said comparison result storing step, while changing said delay time for delaying said test signal in said delay step, and storing said comparison results for each delay time;

a detecting step for detecting a range wherein said test signal delayed in said delay step and said anticipated value generated in said anticipated value generating step match, based on said comparison results for each delay time stored in said repetition step; and

a determining step for determining quality of said receiving unit or said transmitting unit, based on the range of said delay time detected in said detecting step.