In a method of providing a channelclient status register to enable improved channel switching in an Internet Protocol network with a plurality of client nodes each capable of receiving video sessions over a plurality of channels from at least one video provider system, initially arranging S1 said plurality client 5 nodes into an associated group. The droplets are ejected toward sites on a substrate surface for deposition thereon. Some embodiments include producing iron-based catalysts. An optical signal is transmitted between the light-guide device and the upper surface of the plate via the light guiding hole.