This is for synchronisation, for more information about blc_channels, see ( https://git.u-cergy.fr/blaar/blibs/blc_channel/blob/master/README.md ).
output channel
--------------
Example defining a synchronous (':', '/' for asynchronous) channel of unsigned char ('UIN8') of 4096 values with no specific format ('NDEF').
Example defining a synchronous (':' double synchronization, '/' for asynchronization) channel of unsigned char ('UIN8') of 4096 values with no specific format ('NDEF').