What happens to your computer when the power goes out? Hopefully, you have a battery backup device known as an Uninterruptible Power Supply (UPS) that keeps your PC in operation for at least a few minutes. There are three basic types of UPSs and not all are adequate for mission critical communications devices.

Standby UPSs are also referred to as an off-line UPS. This type of unit powers the load directly from the AC source and will only go on-line when the incoming power goes below a preset threshold. After the power sags, or fails all together, a battery-powered inverter kicks in to provide clean power to the load. This causes a momentary interruption of power to the load referred to as "transfer time," which can cause problems with sensitive equipment.

Standby units do not provide conditioning to the incoming power and should only be used on non-mission critical equipment. We do not recommend standby units for our advanced telephone systems.

Line-Interactive UPSs are essentially standby UPSs with line conditioning added. The line conditioning allows the UPS to provide a voltage boost to the load without accessing the batteries. This allows continuous line conditioning, lengthens battery life, and helps to eliminate electronic "noise" that can cause minor application errors and loss of data.

This type of UPS is an improvement over the standby models and works well in most environments, but there are a few drawbacks. There is no frequency regulation. Battery reserve time and recharge time may not be adequate for critical loads. Some units may not be suitable for use with generators.

Online UPSs are double-conversion uninterruptible power supplies. These high-end units completely rectify the AC line to DC, and use this DC to charge the batteries and power a DC to AC convertor to power the load. Since power is constantly going through the inverter, there is no transfer time needed to switch to the battery in the event of a voltage sag or outage.

Under normal circumstances the Online UPS is always "online" providing isolation, filtering, regulation and frequency control. This is the top of the line UPS, which also means they cost more. However, they provide much better power and should be considered for mission critical communication equipment such as telephone systems and servers.

Remember that all UPS units require batteries for reserve power. These batteries should be tested annually and replaced when necessary. The best UPS is only as good as the batteries it runs off of.

North Florida Communications is an authorized Minuteman UPS reseller. If you need help sizing an UPS for your equipment, please go to this web page. If I can assist you in any way, please do not hesitate to contact me.

Larry Nazworth