When your business expands, more users and concurrent calls can be added easily to meet growing business needs through the telephony cards in the IP PBX. U-4FXU can be flexibly configured in PBX-U502/U503 by hot-plug mode to expand its functionality, it supports 4 FXO and 4 FXS per board and any four boards of the same series can be mixed according to your specific needs.
