Automatic transmission systems for television and radio broadcasting

A method of merging playlists each for a single channel for simultaneous transmission over a network by a multi-channel automatic transmission over a network by a multi-channel automatic transmission system (1) replaces the functions previously performed in a network studio (100) by a number of single channel automatic transmission systems (111, 112, 113 ...) corresponding to a number of regional transmitters (101, 102, 103 ...). Any proposed merging is checked before the merged playlist is completed. The checking takes the form of two sequentially applied tests. The first test is that the required number of cassette changes be less than or equal to a calculatable maximum number. The second test is that for each channel, for each event other than the first event on the playlist, the sum of the cumulative thread, cue and pre-roll times and the elevator movement times be less than or equal to the sum of the total event durations including the event being checked less the total of the previous event durations for that channel.