Methods and apparatus are provided for sigma-delta delay control in a Delay-Locked-Loop that employs a delay line to generate a clock signal based on a reference signal. The insulating housing defines a plug insertion hole from a front end to a rear end thereof and a recess communicating with the plug insertion hole. An optical apparatus includes first vibrator for successive vibration with frequencies, a circuit monitoring the state of vibration of the optical element during vibrating operation of the first vibrator, thereby detecting the resonance frequency of the element, and second vibrator for vibration with the detected resonance frequency or a frequency approximate to it. A removable cartridge is disposed within the bearing frame and has a shaft extension connected to the motor shaft. As a result, even if a skew occurs among the transmission channels, correct pixel data is displayed. A solid tire has a hub connecting ring portion that securely embraces and that radially and outwardly extends relative to the upper wings, and a ground engaging ring portion that axially reduces and that radially and outwardly extends from the hub connecting ring portion.