Solution:

We explain this problem as follows: 1. Communication channel: The firmware with V3.9 can support you up to four channels, that means four pairs of 4550s can work well at the same time without interference. You can use 4550 utility with version 2.3 to configure which channel you want to communicate for certain pair 4550s. 2. ID address: Non-addressable mode => No limitation Addressable mode => Because ID address of 4550 is from 00h to FEh and there are 8 different delimeter characters you can select, that means every master 4550 can control 8*255=2040 slave 4550s at the same time.