Specifications

Power Supply Unit Load Requirements

Unit Load Calculation Rules

Mode

Installed

Modules

Calculation

Hybrid/PBX,

Modified Key,

Behind Switch

Not required

Square Key

4 or fewer† Not required

Behind Switch

* The 391A1 power supply unit generally supports 6 modules of

any type in Hybrid/PBX mode. However, if all 6 carrier slots

meet the following conditions, the unit load total may exceed 54

and auxiliary power may be required:

■ Only MLX or analog multiline station modules are installed.

■ More than 45 MLX-20L or 34-button analog multiline

telephones are installed.

t The 391A1 power supply unit generally supports 4 modules