The Cisco Catalyst 3750 Series switches do support the Cisco Redundant Power System (RPS) 675 and the Cisco RPS 300.
Both the Cisco RPS 675 and RPS 300 provide superior internal power source redundancy for up to six Cisco networking devices. This results in improved fault tolerance and network uptime.
In this configuration, if one device has a power-supply or power-related failure, the RPS immediately begins to supply power to this device and is no longer available as a backup power source for the other devices. The RPS sends status information to network management software to alert the system administrator that the other devices are not supported until the failed device or the power supply in the failed device is repaired or replaced.
Note: The RPS is designed to provide backup for internal power supply failures of connected device power supplies. It is not designed to act as a backup power source for external power outages. Use an Uninterruptible Power System (UPS) as protection against loss of power due to power outages.