3 Keys to choosing a surge protector

There are many different kinds of surge protectors. Surge protectors installed on power lines don’t absorb or otherwise diminish damaging power surges. Their primary function is to divert these destructive forces away from your sensitive circuitry.

There are four basic kinds of surge protectors: metal oxide varistors (MOVs), avalanche diodes, filters, and gas tubes.

Metal oxide varistors (MOVs) are a common choice. The word varistor is a combination of two words: variable resistor. As these words imply, an MOV is a highly resistive device that triggers during an AC power surge and diverts the excess voltage, preventing it from reaching your expensive computer equipment.

MOVs are designed to accommodate surge levels up to a specified breakdown voltage. When this limit is exceeded, the MOV varies from a highly resistive state to a state of low resistance. The excess energy is “clipped” from the power line and sent to ground.

Surges occurring at the peak of a sine wave are clipped by the MOV, but high-voltage spikes may still occur (though they’ll eventually be clipped), and the MOV response times can range up to 500 picoseconds. This is the primary weakness of an MOV, but it’s usually overcome by the inclusion of some other suppression technique within the surge protector.

Avalanche diodes, also known as Zener diodes, are semiconductor devices similar to MOVs, but they feature much faster response times (usually less than one picosecond). Avalanche diodes are available in a wider range of sizes to provide accurate and repeatable voltage clamping. However, they have limited ability to withstand large surges, which means they should be combined with other devices to make them useful for lightning surge protection.

Filters are also usually built into surge protectors, along with other suppression devices, to offer enhanced levels of protection. They’re made up of discrete coils, called chocks, and capacitors that are designed to filter noise occurring within specific frequency ranges on AC power lines. Continue reading


How to pick an IT rack

A rack is any freestanding frame that doesn’t have doors or sides. If you need frequent access to all sides of the equipment and cabling, an open rack is more convenient than a cabinet. If your equipment needs ventilation, a rack offers more air circulation than cabinets. With the open design, racks are a good choice in areas where security isn’t a concern, or inside data centers and closets with locked doors. And racks typically cost less than cabinets. There are several things you should consider when choosing a rack.

Types of racks.
The best place to start when picking a rack is to ask yourself: Where will it be located and what equipment will be in it? This will help you determine if you need a wallmount or a floor-mount model and whether you need a 2-post or 4-post rack.

You have a number of options depending on the type of equipment you need to house. If you’re installing patch panels, a two-post rack with some cable management is the right choice. But if you have a mix of networking equipment, servers, and patch panels, then a 4-post rack makes more sense because it provides more stable, 4-point mounting for deep equipment. Accessories are available which allow you to mount both standard and extra-deep equipment.

Rack widths.IT-Rack
The main component of a rack is a set of vertical rails with mounting holes to which you attach your equipment or shelves. Most racks come in rails spaced at the standard 19″ with hole-to-hole centers measuring 18.3″. To rackmount smaller equipment, add rackmount adapter brackets. For mounting older legacy equipment, there are 23″ wide racks.

Two-post racks typically have threaded 12-24 or 10-32 holes for quick installation of patch panels, and 4-post racks usually have M6 square mounting holes for mounting servers.

Rack heights.
Height, or rack units, is one of the most important specifications in choosing a rack. One rack unit (1U) is 1.75″ of usable space. So, for example, a rackmount device that’s 2U high takes up 3.5″ of rack space. Most freestanding racks come in a standard 45U height, which is 6.5 feet high, so they fit rooms with standard ceilings. But there are other height options— from smaller 10U-high wallmount models all the way up 58U-high units. These tall racks, towering up to 9 feet, allow for an extremely dense installation of equipment while saving floor space. Continue reading

How to terminate your own patch cable

Of all the components in your network, none is arguably more underrated than the RJ-45 connector. Simplicity incarnate, this transparent marvel literally defines plug-and-play connectivity—from the desktop to the data center. Yet it defies the obvious: How’d they get those wires in there? Who puts these things together? Where are the seams?

So, in the spirit of demystifying one more aspect of modern-day communications, we give you this behind-the-scenes look at terminating twisted-pair cable using RJ connectors.

The prep work.
First, gather your materials. You’ll need bulk cable, such as the GigaTrue CAT6 550-MHz Solid Bulk Cable, a cable cutter and stripper, a connector, a pre-plug (optional), a crimp tool, and a continuity tester. All these items—except the cable and the pre-plugs—are in our CAT6 and CAT5e Terminations Kit.

The challenge: Do it right the first time.
You must take time to install each connector carefully, according to the specifications of the wiring system you’re installing. Then test each cable to certify that it supports the specified performance levels — in this case, the TIA specs for CATx cabling. The wiring standards illustration (above right) indicates proper T568A, T568B, and USOC pairing and pinning for twisted pair cable. T568B wiring is most commonly used in North America for networking. Continue reading

Every security system must-have: Fallback power switches

In this security-conscious age, webcams, motion detectors, and badge scanners have become increasingly common elements in most businesses and public facilities. It doesn’t matter if you’re checking ID cards, observing activity in a lobby or community space, or monitoring a building during off-hours for suspicious activity; most mission critical security applications rely on the sort of constant vigilance that can only be supplied by a monitoring device, ID scanner, or electronic sensor.

An intelligently planned electronic security system can monitor badge-in/ badge-out activity, detect movement in buildings during non-work hours, generate alarms when doors are opened in secure areas, and keep watch over huge buildings without the need for regular patrols by ever-present security personnel.

But as useful as these devices are, it’s important to remember that many electronic sensors and monitoring devices do not include power fallback capabilities, and as such, they can often be rendered useless by a simple power interruption. This means that even if your security solution includes the most advanced equipment available, without a reliable power fallback solution, your building can still be left unprotected during a power outage or blackout—or when external power to the security system has been purposely defeated.

Fallback Power Switch, 240-VAC

Fallback Power Switch, 240-VAC

If your security system or access control application lacks an effective power redundancy solution, fallback power switches can provide fast, reliable power fallback capabilities, without the need to replace existing single power inlet devices with new, dual-inlet devices. The switches can help to minimize or eliminate downtime for your security system by ensuring that even when your main power source is not available, the security system can automatically switch over to a back-up power source almost instantaneously. Continue reading