There is only one physical serial port on the box.
Output of the setserial command:
[root@freepbx ~]# setserial -g /dev/ttyS[0123]
/dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4
/dev/ttyS1, UART: unknown, Port: 0x02f8, IRQ: 3
/dev/ttyS2, UART: unknown, Port: 0x03e8, IRQ: 4
/dev/ttyS3, UART...