A system comprising a plurality of apparatuses for processing user information and being arranged with inputs and outputs that have dedicated point-to-point interconnections for communicating such user information between said apparatuses, said apparatuses being furthermore linked by a serial control channel,
- said system having cable detection means addressable via said serial control channel for automatically detecting said point-to-point interconnections through generating a sequence of a first message, a subsequence of second messages, and a third message, each said input being provided with a detector for such user information,
- said first message interrupting any supply of user information to any said interconnection,
- each message of said subsequence of second messages enabling the supply of user information to one interconnection unique to that message while interrupting any further supply to other interconnections and thereby activating at most one unique detector, a time-sequential detection pattern of all detectors thus identifying said interconnections,
- said third message re-enabling the supply of user information to all said interconnections.