Distribution of network configuration specific commands

A control system for issuing local commands selectively to a plurality of zones e.g. for operating selected doors of a train. A command system 14 generates a command containing information relating to the zones to which a local command is to be issued, a transmission medium 16 transmits the command, and a plurality of blocks 12 are connected in series by the transmission medium, each block assigned to one of the zones. Each block 12 receives the command, issues a local command to the zone if required by the command, modifies the command to account for receipt of the command by the block, and transmits the command to a subsequent block in the series. Different alternative command structures are described: using one wire per zone; binary coding (multiplexing); or serial communication. Each block may modify the command by decrementing the indication of the number of zones to which the local command is to be issued, e.g. by decrementing the number of signals transmitted in parallel, or the number of pulses in a train.