This was the first version of Master Control Link and was used with the Beosystem 5000 and the Beocenter 7000 series.
It allowed control of all elements in the main system whilst in a link room. The first incarnation was used with the remote controls of the Beosystem 5000 and Beocenter 7000 and when used with the MCP-5000 and MCP-7700, allowed two way communication. One could add four rooms in this system. It was superseded by the later MCL2 system which used Beolink 1000 codes.