Cat3 ISDN panels are loaded panels for terminating voice and PBX lines at high port density, offering up to 25 or 50 ports in a 1U body. Class C at 16 MHz is inadequate for data, but it markedly lowers cost per port for analogue lines, ISDN and PBX distribution. When they share a cabinet with data cabling, keeping voice and data panels physically separated prevents mis-patching during maintenance.