Presumably short for Roland Buss. R-Buss is a connectivity scheme (or bus scheme) developed at Roland for interfacing their digital mixer and recorder products with one another. The idea is for one cable to carry all necessary signals between units so an R-Buss cable can carry eight channels of digital audio with word clock as well as transport and location information. Two 8-track Roland recorders can thus be connected to each other with one R-Buss connection, and they can each be connected to a compatible Roland digital mixer with one R-Buss connection each. Roland also manufactures interfaces for ADAT and other popular MDM and DAW formats so they can be integrated with a Roland mixer using R-Buss.