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4.1 Noise and surge suppression
The UPS contains high performance EMI/RFI (Electro-Magnetic and Radio Frequency
Interference) noise and surge suppression circuitry to protect your computer equipment.
The UPS provides this suppression continuously, whether or not it is turned on. Nor-
mally, the UPS will continuously filter surges and electrical noise without using the battery
charge. The suppression circuitry will reduce the amplitude of these power disturbances
to conform to the strict requirements of all modern computing equipment.
The illustration above shows what a typical “medium” amplitude surge or spike looks like
when present on the utility voltage. Surges up to 15 times larger than this are easily
suppressed by the UPS. Surges are commonly caused by nearby lightning activity and
motor load switching created in air conditioners, elevators and heat pumps.
The illustration above shows what EMI/RFI noise looks like when present on the utility
voltage. The UPS “filters” out this noise with components whose electrical resistance is
very high at radio frequencies. EMI/RFI noise is commonly created by the same activity
which produces surges but can also be caused by nearby radio transmitters and blinking
neon bulbs and signs.