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APC AP7921

AP7921 is a 1U 8-outlets switched PDU from APC.

  • No per-out metering.
  • Outlet is C14; Input is C20.
  • Although spec says 220V input, 110V also works.
  • AVR control plane.
  • Only supports old cipher like 3DES.
  • The meter precision is lower than AP7921B.
  • The console is menu-based and is pretty hard to use (AP7921B is console-based).

Console Cable

AP7921 has a reset button, but it only allows temporary logon to the serial console via default username and password (apc / apc). It won't reset web portal password. Thus, you have to get a console cable if you loss the password.

Even worse, APC uses the wired RJ12 connector for console rather than RS232 or RJ45. Instead of buying a cable, I highly recommend you to make your own.

Ingredients:

  • RJ12 male connector: Must be 4pin / 6pin. 2pin RJ11 won't work.
  • RS232 female connector

Wiring:

  RS232 F      RJ12 M
                ┌──┐
┌─────────┐    ┌┴──┴┐
│5 4 3 2 1│  ┌─┘    └─┐
└┐9 8 7 6┌┘  │ 654321 │
 └───────┘   └────────┘
Female 5GND     Male
     Front  Facing
 GND 5──────────5
  TX 2───────────4
  RX 3────────────3
 GND 5─────────────2

Taken from pinoutguide.com/UPS/apc_940-0144a_cable_pinout.shtml but swapped RX and TX.

Serial parameters:

  • Baud rate: 9600
  • No stop bit

You need to press enter several times for the login prompt to show up.

Last update: November 9, 2023
Created: November 5, 2023