A motor control device coupleable to a host controller for controlling a motor of a cooling blower, the motor control device being configured to control the motor of the cooling blower based on a first PWM signal (Si) being received from a host controller if the host controller is coupled to the motor control device, the motor control device being coupleable with the host controller via two PWM signal lines (19a, 19b), the motor control device is configured to receive the first PWM signal (Si) from the host controller if the host controller is coupled to the motor control device, and the motor control device is configured to transmit a second PWM signal (So) to the host controller via the two PWM signal lines (19a, 19b) if the host controller is coupled to the motor control device, the motor control device comprises: a PWM-signal detecting unit configured to detect a PWM frequency and a PWM duty ratio of the first PWM signal (Si); and a PWM-signal generation unit; characterized by: the motor control device is configured to receive the first PWM signal (Si) including the target rotating-speed command from the host controller via the PWM signal line so as to control the cooling capacity of the cooling blower if the host controller is coupled to the motor control device; a request-pattern determination unit configured to determine whether the first PWM signal contains a destination-signal (Si) request pattern for requesting a destination signal pattern to specify destination for the cooling blower, based on an output of the PWM-signal detecting unit; and wherein the PWM-signal generation unit is configured to generate the second PWM signal (So) based on a determination result of the request-pattern determination unit; wherein the PWM-signal generation unit is configured to generate the second PWM signal based on the destination signal pattern when the destination-signal (So) request pattern is contained, or wherein the motor control device is configured to be notified of a target rotating-speed command, as a command from the host controller, which commands a target rotating speed (Vr) of the motor, when the destination-signal request pattern is not contained, and wherein the PWM-signal generation unit is configured to generate the second PWM signal (So) based on an actual rotating-speed information of the motor so as for the host controller to receive a detected rotation speed (Vd) of the motor as the actual rotating-speed information if the host controller is coupled to the motor control device, wherein the PWM-signal generation unit is configured to transmit the generated second PWM signal (So) to the host controller if the host controller is coupled to the motor control device, wherein the motor control device further comprises a rotation controller, wherein the motor control device is configured to determine a speed deviation between the target rotating-speed (Vr) and the detected rotation speed (Vd) by the rotation controller, and wherein a feedback control loop is formed which controls the rotating-speed of the motor to follow the target rotating-speed (Vr). a PWM-signal detecting unit configured to detect a PWM frequency and a PWM duty ratio of the first PWM signal (Si); and a PWM-signal generation unit; the motor control device is configured to receive the first PWM signal (Si) including the target rotating-speed command from the host controller via the PWM signal line so as to control the cooling capacity of the cooling blower if the host controller is coupled to the motor control device; a request-pattern determination unit configured to determine whether the first PWM signal contains a destination-signal (Si) request pattern for requesting a destination signal pattern to specify destination for the cooling blower, based on an output of the PWM-signal detecting unit; and wherein the PWM-signal generation unit is configured to generate the second PWM signal (So) based on a determination result of the request-pattern determination unit;