WS-C3750X-48P-S

                                                                                                     Figure 1

Cisco Catalyst 3750-X Series Switches support 4 optional network modules for uplink ports (Figure 1);
The default switch configuration doesn't include the uplink module; 
When purchasing switch, customers have flexibility to choose any group of network modules described below:

Product Number	Product Description
C3KX-NM-1G	Four GbE port network module
C3KX-NM-10G	Two 10GbE SFP+ ports network module with four physical ports with two SFP+ and two regular SFP ports
C3KX-NM-10GT	Two 10GB-T ports network module
C3KX-SM-10G	Service Module with two 10GbE SFP+ ports network module for Netflow and MACsec encryption

                                                                                              Figure 2

Dual Redundant Modular Power Supplies

Cisco Catalyst 3750-X Series and 3560-X Series Switches support dual redundant power supplies (Figure 2);
One power supply is shipped with the switch by default;
Other power supply/suppliers can be purchased when ordering the switchnext time according to your needs.
If only one power supply is installed, it should always be in the power supply bay 1.

Table below shows the different power supplies available in these switches and available PoE power.

Power Supply Models

Besides the above power supplies, a 440W DC power supply is available as a spare (should be ordered separately) on all switch models;
The DC power supply also delivers PoE capabilities for maximum flexibility, (please refer to table 7 for available PoE for different configurations);
Customers can mix and match the AC and DC power supplies in the two available power supply slots. Any of these power supplies can be installed in any of the switches.

Available PoE with DC power supply