Liebert Autochangeover Controllers AC4 用户手册

The AC4’s controller board has connectors for four digital inputs and four digital outputs, as shown 

below. The board comes complete with light emitting diodes (LEDs) to display the status of connected 

devices, a serial communications port, a power connection and other features necessary to control 

your operation.

Power switch for the controller board.

Provides audible notification when an alarm occurs.

N/A

Jumper to disable the audible horn (factory default is 

enabled).

N/A

The two common alarm connections are used to connect to 

a secondary warning device such as a horn, light or 

Building Management System (BMS). When an alarm is 

present, the contacts close and the external warning device 

is activated/notified. The common alarm contacts may be 

configured to be reset with the Silence button/command. 

Each output has an LED to indicate its status: ON/OFF 

(energized/de-energized).

Placing the switch in the ON position will turn ON, or 

energize, all four outputs simultaneously. This switch 

removes all automatic output control from the AC4.

Each of the four output connections is a two-state point: 

ON/OFF (energized/de-energized).
An example of a field digital output is a Liebert 

Environmental unit’s remote shutdown input. 

Indicates the operational status of the controller board.