A projection zoom lens projects an optical image of rays, which are irradiated from a light source onto a light valve and are modulated by a predetermined image displayed on the light valve, onto a screen. The power supply of the different groups is provided sequentially, each group being powered once per sequence. Upon receiving a message addressed to one of the nodes, a router can tunnel the message to a router on the node’s foreign sub-network for subsequent de-tunneling and delivery to the node.