The BMC application running on the PXS is designed to eliminate
remote polling using a synchronous, half-duplex modem. This means that the
PXS must be able to control 3 input signals to the switch:
DCD. Since each PXS port has only 2 output signals (
RTS), outputs from both ports are used, requiring a special cable.
The special cable combines RS-232 signals from the 2 PXS ports into a single DB-25 connector wired as a null-modem cable.