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-4DTU, E1 telephony card for European Term, can be flexibly configured in PBX-U502 by hot-plug mode to expand its functionality, it supports 4 E1 per board and any four boards of the same series can be mixed according to your specific needs.