The speed was a side effect of Nortel using a 2-wire cable to carry both voice and switching commands, as opposed to other systems where the command data was carried on a separate set of low-speed lines.
Switch56 was built on top of the basic Nortel hardware to allow computers to put data into the existing telephony network.
Although slow compared to even contemporary systems, Switch56 allowed network traffic to flow not only within an office like other LAN systems, but between any branch offices that were connected using a Nortel PBX like the Meridian Norstar.
This was a much easier option to install than ISDN for most offices, requiring nothing more than a Switch56 bridge to their existing network.
For the LAN role new telephone terminals were produced with a RS-232C port on the back, which were then plugged into the user's computer and used with custom software.