Dear user!
If the overhead bytes pass through the backplane bus between two slots, the two slots are paired slots. Paired slots achieves automatic transparent transmission of overhead bytes such as K bytes, D bytes, and E1 overhead bytes. This improves multiplex section protection (MSP) switching performance and protects orderwire and DCC communication with other NEs even after the system control board on the local NE cannot be detected.
Of course, if you don't do protection mainly, or there is only one NE in the entire network, the paired slots are meaningless.
I hope my answer is helpful to you!