A routing matrix contains two type of chassis:
There is only one TX Matrix platform per routing matrix. It is referred to as the switch-card chassis (scc) in the JUNOS CLI.
There can be one to four T640 routing nodes in a routing matrix. These are referred to as line-card chassis 0 through 3 (lcc0–lcc3) in the JUNOS CLI. The T640 routing node number is set by the hardware. See the TX Matrix Platform Hardware Guide for further information on installing and connecting the hardware.