IBM 8271 Nways F12 User Manual page 45

3 Connect the Matrix Cables, as shown in Figure 2-4:
a Connect a Matrix Cable to the port marked Unit 1 on the Matrix
Module. Connect the other end of this cable to the matrix port of
the Switch that contains the Matrix Module.
b Connect a second Matrix Cable to the port marked Unit 2 on the
Matrix Module. Connect the other end of this cable to the matrix
port of the second Switch.
c Repeat steps a and b for any additional Switch units.
A stack of multiple units
Figure 2-4
Stacking Units 2-7