Select which component you would NOT expect to find within a Power Distribution Unit that feeds critical power to server racks within a data center.

In a Power Distribution Unit (PDU) designed for feeding critical power to server racks within a data center, the primary function is to manage and distribute electrical power. Components typically found in a PDU include devices that help in transforming voltage levels, protecting against surges, and ensuring reliable power delivery.

A transformer is often included to adjust voltage levels for appropriate distribution to various equipment. Surge suppression devices are critical for protecting server equipment from voltage spikes, ensuring the reliability and durability of sensitive electronics.

A communications server, however, is not a standard component of a PDU. While it may play a role in managing data center operations, it does not serve the function of distributing or transforming power directly. Instead, it usually exists as a separate entity within the data center infrastructure, managing data and workloads rather than power distribution.

The transfer switch is integral to power management in some situations, particularly for ensuring alternate power sourcing, but it is not a component typically found within a standard PDU focused exclusively on electrical distribution. Thus, its absence from the expected components of a PDU can be clearly understood, whereas the inclusion of the transformer and surge suppression aligns directly with the PDU's purpose.