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Standby Power Supply (SPS)


A Standby Power Supply (SPS) contains a battery, a switchover circuit, and an inverter (a device to convert the DC voltage from the battery into AC voltage that the computer and peripherals need). The outlets on the SPS


are connected to the switching circuit, which is in turn connected to the incoming AC power (called line voltage). The switching circuit monitors the line voltage. When it drops below a factory-preset threshold, the switching circuit switches from line voltage to the battery and inverter. The battery and inverter power the outlets (and, thus, the computers or devices plugged into them) until the switching circuit detects that line voltage is present again at the correct levels. The switching circuit then switches the outlets back to line voltage.

Level of Protection


SPS can provide some protection against power outages (more so than surge protectors, at any rate). Unfortunately, because the switching circuit must switch between power sources, there is a short period of time when the outlets have no power. Computers and network devices can usually handle this infinitesimally short period of time without power, but they don’t always handle it gracefully. Some devices will lock up or experience errors. Others can even reboot (thus negating the reason for having a battery backup system).


For this reason, SPS has never been really popular with computer and electronic equipment users. They are inexpensive and they can provide a basic level of protection, but this is usually not sufficient for sites that require 100-percent uptime.

Common Components/Features


Most Standby Power Supplies will have one or more of these features or components:

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