A single Master controller (R CT 5030 / R CT 5031) can support up to 15 x R CT 5020 / R CT 5021 Rack 

controllers via the CONTROL sockets. Total cable length for all connections is 250m in RS 485 mode.

Up to seven additional racks (with R CT 5010 controllers) can be daisy-chained onto a single R CT 5020 / R CT 5021 via the EXTEND socket. 

Total cable length for this connection is limited to approx. 1.5m in the R FR 5010/5011 and approx. 

10m in the R FR 5012.

For further information please have a look at the manuals for the LYNX rack controllers.