To use multiple Reply systems simultaneously, each system must use a different channel. Also, you need multiple Com Ports, one for each Reply system.
Virtual Numbering
Since each interface can address up to 250 keypads and all keypads use individual addresses between 1 and 250, PowerCom will convert physical keypad addresses to virtual addresses for all Com Ports after the first.
Keypads associated with your lowest number port remain numbered 1-250. Any keypads on your next port are assigned virtual addresses of 251-500. The next port will be assigned 501-750, etc. So for example, if you are using two interfaces (Channel 1 and 2) with 125 pads for each interface numbered 1-125, PowerCom will report your keypad numbers as 1 to 125 for interface 1 and 251 to 375 for interface 2. Note that there are no keypads numbered 126-250.
If you do not understand this and you are using more that one system, stop and re-read it carefully. It is important to understand this concept because you will need to physically re-label your keypads according to PowerCom's Virtual Numbering Plan.