Technical Note: First Published 19 May 2016

The following cable is used to connect to the APC AP7920 rack mounted power distribution units. Other models will also be covered by this cable, but have not been tested by the author.

A 6 pin RJ12 connector is used on the front panel of the PDU, to allow an RS232 serial connection for management and configuration. This is usually only necessary during first configuration or password recovery, as once up and running all access can be made via a web browser.

Cable Wiring

A 4 way flat cable can be used in the connection as the outer two cables are not used.

RJ12 (6P6C)	Pin Number	Function	Direction	Pin Number	9 way D socket
	1	Unknown			Viewed looking in to the mating face.
	2	Ground		5
	3	Receive Data	←	2
	4	Transmit Data	→	3
	5	Ground		5
	6	Unknown

Either of the Ground connections on the RJ12 can be used – they also do not need to be interconnected.

Usage

1. Ensure that the AP7920 is powered up and fully started (this can take over a minute from power on).

2. Connect to a host by using the above cable and a free serial port set at 9600 baud, 8 bits and no parity. Flow control is not used.

3. Press and release the Reset button on the PDU.

4. Wait for the orange LED to start flashing.

5. Press the reset button again whilst it is still flashing.

6. Press ‘return’ to get the username prompt.

7. The serial console will now be active for 30 seconds – log in using the username/pass word of ‘apc’ and ‘apc’ (without the quotes)… It stays active once logged in.

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