This is achieved by means of composition, with the transducer TopChannelNotEmpty defined as follows: TopChannelNotEmpty =~[ ["<" LeftChannelSymbols* "0" "(" AnyIG ("@") ")" "0" RightChannelSymbols* ">" ] *] ; This filter would be read as "It is not the case that all topmost channel symbols in a configuration are all 0s."
configurations in which all most recent channel symbols are 0 are filtered.