In a phase-locked loop, a desired change in frequency is indicated. The incident element has a first reflective portion formed with a closed circumferential surface, an image inlet and an image outlet that incorporate with the first reflective portion to form an image transmission passage. Compounds of the present invention have the following formula:. Reference counts for the first sub block and a second sub block are lazily updated. The present invention provides a multimedia search method enabling to measure the similarity between features quantized into different levels. A method for transmitting signal comprises generating a short training field comprising a cyclic prefix and an effective symbol period including four RP regions; generating a long training field comprising a cyclic prefix and an effective symbol period including two RP regions; generating a frame comprising the STF and the LTF; and transmitting the frame.