As a rule-of-thumb, one PSU-101 power supply unit is required for every two IMF-3 frames. There are some exceptions to this rule. 

The exception occurs when using multiple TEL-14 telephone interfaces. An IMF-3 interface frame will only power eight TEL-14 interfaces. If more TEL-14 interfaces are required, you must install them in a second IMF-3 frame with a second power supply.

A PSU-101 requires 90 to 260 VAC at 45 to 65 Hz with a maximum dissipation of 80 W. A PSU-101 connected for redundancy requires very little AC current unless it is used. Installing two PSU-101 power supplies per application provides redundancy because either of the two PSU-101 power supplies can power a complete system. If one fails, it can be removed without interruption of the entire system. Rear panel connectors provide easy parallel connection to the IMF-3 Interface Module Frame.

The current capacities of the power supplies are as follows:
• 9 V analog 3.0 amperes
• -9 V analog 3.0 amperes

The chart below provides the current drain of the +/- analog power supplies for all components in the system. Some devices, such as interfaces, have a varying current depending on the operation of features. In applications where it is possible to activate all operating features of all components used, use the maximum current column for planning.

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