You'll generally have too many devices at a site to plug them all directly into your power supply. You need PDUs to distribute your site's power to each device. This is possible because a PDU turns one (or a few) power inputs into many (usually about eight) power outputs.
PDUs are available in both AC and DC models to match the power in use at different kinds of sites.
Now let's add another layer to our definition by adding the word "rack". A "rack PDU" is a PDU that is designed to be mounted in an industry-standard equipment rack. These are typically either 19 inches or 23 inches in width. Height can vary from PDU to PDU, but most are just one "rack unit" high. This translates to about 1.75 inches.
A rack PDU is different from other kinds of PDUs that are designed to be wall-mounted or attached to the side of an equipment rack. These other PDUs conserve valuable physical rack space in cramped equipment racks, but they do increase the distance between the power outputs of the PDU and the power inputs of the devices that will receive electricity.
Now that we know what a rack PDU is, let's take a look at the phrase "switched PDU". Switching, in the PDU context, means toggling power on and off for individual power outputs.
Switching opens up a whole new world of remote management possibilities for your servers and other devices. Now, with a few clicks or keystrokes, you can remotely reboot servers, activate backup systems, power devices down ahead of a flood or other natural disaster, and perform other valuable power control functions.
This is why a switched PDU greatly enhances your ability to remotely manage power to your devices.
OK. Let's put it all together. A "switched rack PDU" combines the strengths of a rack PDU with those of a switched PDU. This kind of power distribution unit is designed to be installed in your equipment racks to distribute power to your telecom equipment. In the event that you need to turn on, turn off, or reboot one of your devices, you can use the remote switching functionality of your switched rack PDU to handle that task from your desk - without driving to the site.
By installing in industry-standard equipment racks, switched rack PDUs allow for a very clean and professional installation. With remote switching functions, switched rack PDUs dramatically reduce the costs associated with driving out to sites just to activate or reboot a remote device.