... A value can be given for every channel. ... Note that BBC assignments are arbitrary for the RDBE and the old VLBA systems since all BBCs can see all input IFs. However, for Mark III and Mark IV systems and the current version of the DBBC, there are strong constraints. For Mark III/IV ``astronomical patching'', which is the only one currently properly understood, the odd BBCs must be connected to IF1 (IFCHAN 1N or 1A where 1N is normally LCP and 1A is normally RCP). ...