A drive power transmission device is disclosed having a drive mechanism for transmitting a drive power between first and second rotary members rotatable relative to each other, by the operation of an electromagnetic type clutch mechanism which brings a friction clutch into connection. The congestion reduction method comprises steps of receiving a DHCP request from a DHCP client; and stopping responding to a certain number of DHCPDISCOVER message. Tie present invention is applicable to both speech coding and natural audio coding systems. The method further comprises generating color frames corresponding to the scene at a frame rate higher than a frame rate of the first set of frames based at least in part on processing of the first set of frames and the second set of frames. The sensor may be adapted to detect the presence of the perpetrator in a target area of the marker delivery device.