What is Huawei SLQ16 board substitution relation among different versions?

SLQ16 is a 4 port STM-16 optical interface board, can be used on Huawei OSN 3500, OSN7500. SLQ16 comes with 4 unit SFP module.

When the AU-3 services and TCM function are not required, Huawei N1SLQ16 and N2SLQ16 can be substituted with each other. The N4SLQ16 supports the board version replacement function to substitute for the N1SLQ16/N2SLQ16.