Control information associated with data bursts to be switched on a burst-switched router is transmitted using payload envelopes on one or more control channels. An event entered through an event input means 4 is given to a delivery destination determining means 6 which in turn determines to which of applications AP1, AP2,. The controller may be integrated with existing controller schemes to provide superior dynamic performance during large-signal transient conditions while providing stable operation during steady state conditions. The card holder control mechanism includes a knob and a rotatable plate.