3Com 8800 manual RS485 and RS232 signals are described in and Table, Pin Definition

System Controller 11

■Monitor system operation status - An AC sensor card inside the PoE Power Rack samples the AC input voltage. The sampled signal is sent to the controller for processing. If the AC input voltage is lower than the pre-set alarm level, the controller reports an AC input under-voltage alarm. Likewise, if the input voltage is higher than the pre-set alarm level, the controller reports an AC input over-voltage alarm. The DC output voltage is also sampled and sent to the controller. If the output voltage is lower than the pre-set alarm level, the controller will report a DC Low alarm. Likewise, if the DC output voltage is higher than the pre-set alarm, the controller reports a DC output High alarm. The power supply module status communicates with the controller via an internal RS485 bus. If the power supply modules issues an alarm, the alarm is passed to the controller. Power supply module failure alarms include: AC input failure, DC output failure, fan failure, high output voltage, current limit, over temperature, and module shut-down.

■Communicate with deamon systems - The controller supports interface to the Switch 8800 chassis through RS232 or RS485 cable connection. A cable is provided with the PoE Power Rack for attachment to the Switch 8800 (connect the RS232 connector end to the PoE Power Rack and connect the RJ45 cable end to the port labeled "Com" next to the PoE DC terminal block on the back of the Switch 8800). Using CLI commands, the user can receive and read system information or command the operation of the PoE Power Rack. The RS485-1 and RS485-2 have the same function. The customer can choose only one port for communication. The RS485/RS232 can not work at same time, so do not connect them both at the same time.

There is one RS485 port and one RS232 interface on the rear panel of the PoE Power Rack (the cable provided with the PoE Power Rack is a RS232 cable type).

The RS485 and RS232 signals are described in Table 3 and Table 4. :

Table 3 RS485 Pin Definitions

Pin	Definition
1	Transmit, +
2	Transmit, -
3	Receive, +
4	Ground
5	Not used
6	Receive, -
7	Ground
8	Not used

Table 4 RS232 Pin Definitions

Pin	Definition
1	Not used
2	Receive
3	Transmit
4	Not used
5	Ground
6 - 9	Not used