A twisted string actuator system includes a motor generating rotary motion of a rotor and a twisted string comprised of a pair of cords. When the residual amount is less than a predetermined amount, a warning is displayed to a user in order to replace the battery. The memory and the computer program code are configured to, with the processor, cause the apparatus to allocate a time-division duplex carrier for a frequency-division duplex downlink signal for communication with a communication element, and employ the time-division duplex carrier with a truncated time duration for the frequency-division duplex down-link signal.