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568A has the green pair at pins 1 and 2 and the orange pair at pins 3 and 6; 568B is installed in the reverse. The blue and brown pairs remain the same.

All Category 5 cable is rated for 100Mb/sec - Category 3 is rated for only 10.

All Category 5 cable is unshielded twisted pair.

Not only does each pair in the cable have a slightly different twist than the other pairs, the specification does not demand a certain number of twists per foot; only that a cable allotted the rating "Category 5" meets the Category 5 standards without regard to the particular method of construction.

It takes pressure, or voltage, to push electrons through a wire. Too much cable length without enhancing a signal in some way uses up that pressure and reduces the strength of a signal at the receiving end.

Interference between pairs of wires in the cable is called crosstalk.

Ballasts, transformers, and motors create electrical fields that can interfere with signal integrity, but will not necessarily attenuate or weaken the signal.

The rating on any cable refers to its ability to transfer data at a certain rate of speed, not the distance involved. The standard for Category 5 UTP to meet is 100Mb/sec over 100m; any properly installed UTP cable that can deliver that performance receives a rating of Category 5.

Because of the electrical shielding around the wires, STP may be a better choice in an environment where exposure to inductance fields and flux are unavoidable.

The shielding in STP results in a stiffer cable, and a bend radius that is too tight may damage the shielding as well.

STP is more expensive than UTP by a good margin and thus this is a disadvantage of STP when compared to UTP.

STP must be properly grounded at both ends, or the shielding actually becomes an antenna and backfires in the stated intent by picking up outside signals and radiating them into the wires.

The connectors used for coaxial cable are much faster and easier to attach to a cut cable end than those used for UTP/STP or fiber optic (with the right tools).

While this is true-10Base2 is capable of carrying a signal 185m and 10Base5 will handle 500m, as opposed to the 100m allowed by UTP/STP-very few homes will ever require a continuous 330-foot run.

Ethernet thin coax (RG-58) and TV cable coax (RG-59) have different impedances (50 ohms and 75 ohms, respectively); using either in the wrong place will cause problems.

Coaxial networks are almost always based upon a bus topology; NICs, hubs and switches that will accept coax cable are nowadays difficult to find.

The "10" in 10Base2 and 10Base5 stands for 10 Mb/sec. Cat5 UTP handles 100 Mbps.

Both the bus topology and the daisy-chain idea work on the principle of having all devices connected along one backbone cable, exposing the entire system to becoming disabled with one wiring fault. It is however the fastest, easiest, and cheapest method, and may not be a bad choice for a temporary setup. However, the bus technology should be avoided for long term solutions.

The Star topology makes use of a central hub connecting all devices or nodes to it; there is no direct connection between devices. This provides for high fault tolerance and easier isolation of network problems... unlike the daisy-chain.

The Ring topology connects nodes in a virtual circle. Like the daisy-chain, each device has only two "neighbors", but a cable break can occur and leave the system still operational-though in Bus mode. Often two "counter-rotating" rings are used, as in fiber systems, for increased fault tolerance.

A Mesh topology physically connects all nodes to all other or several other nodes without a central hub device. This is great for fault tolerance but expensive in terms of cable and connection usage, and is the complete opposite of a daisy-chain, where only one route between nodes exists.

Plenum cabling is designed to be installed over suspended ceilings and other fire-sensitive spaces without presenting additional hazards such as toxic fumes and flammability. It is usually marked as FT-6 and/or CMP.

A special Romex NM type cable marked U/F (underground feeder) is used in buried power lines, not plenum.

Fiber-optic cable transmits signals by pulses of light instead of electricity.

UTP Category 6 is designed to meet the demands of Gigabit Ethernet.

A dimmer switch uses a rheostat, or variable resistor, to regulate the amount of current reaching a lighting appliance.

A motion detector uses infrared sensors, not a variable resistor.

Smoke alarms use a photoelectric device or an ionization chamber, not a variable resistor.

A thermostat uses a solid-state thermal sensor (thermistor) or a bimetal strip, not a variable resistor, to detect changes in temperature.

The "NM" stands for non-metallic, which sets Romex apart from conduit or MC armored cable. In fact, a type of Romex called U/F (underground feeder) is suitable for underground use-outdoors.

The 12 in the specification refers to the size, or gauge, of the wires (AWG - American Wire Gauge).

The 3 in the specification is the number of current-carrying wires (3-conductor), and does not include the fourth wire used for grounding.

Local codes vary, but the 12 in the specification indicates 12 gauge wire, which is suitable for carrying the heavier-duty 220 voltage that some appliances (such as ranges and dryers) utilize.

Black wire hot, white wire neutral, red wire hot, and bare wire ground is the conventional scheme. Always assume that a red wire (if present) is "hot", or carrying juice.

It is a big mistake to consider the black wire ground. The black wire is ALWAYS "hot", or actively carrying juice if the circuit is functional. The white wire may or may not be carrying voltage.

Both red and black wires should always be assumed hot, or energized, rather than unused "spare." Green ground wires may be present in appliances, but in a Romex cable the ground wire is bare copper.

The red wire (if present) should be assumed hot, rather than neutral. White wires are neutral, or return, and every modern Romex cable has a bare copper wire used for grounding.

A Ground Fault Circuit Interrupter device must protect any exterior AC outlet, and any AC outlet within reach of plumbing fixtures such as in kitchens and bathrooms.

A Ground Fault Circuit Interrupter device must protect any exterior AC outlet, and any AC outlet within reach of plumbing fixtures such as in kitchens and bathrooms.

A Ground Fault Circuit Interrupter device is not automatically required for a 220 volt outlet.

A Ground Fault Circuit Interrupter device is not required when adding an outlet to a previously existing circuit unless it is an exterior outlet or located near plumbing. It would be a good idea, though, to check the circuit breaker's rating.

A dry, indoor location does not require a GFCI circuit or device.

Customarily when a receptacle is switch-controlled, only one of the two outlets is wired separately; the other is always "on". This may also be required by code.

Only the hot connection between the two outlets in the receptacle box should be interrupted; they may share the neutral wire.

Wiring both outlets in the receptacle box separately, through the wall switch may not allow the receptacle to "count" as part of the code-required number of outlets in a linear run of wall.

Breaking off both "ears" inside the receptacle connecting the two outlets would require an unnecessary amount of cabling.

Both ground and neutral "go" back to the same place regardless of where they start; connecting the ground wire and the neutral wire separately for each of the two outlets in the receptacle accomplishes nothing.

Each conductor wire supplies 110 volts to the outlet, for a total of 220.

Wiring 2-way switches that control the same device from different physical locations is where 3-conductor cable really shines; using it minimizes the amount of cabling required to have a wall switch at either end of a hallway control the same light fixture.

Installing a ceiling fan with an attached light fixture can be done, but is not necessary or usual. Unless the ceiling fan is completely out of reach, control of the separate devices is obtained by pair of pull chains. A 3-conductor cable is unnecessary unless the light fixture is connected to a dimmer switch-not a good thing to involve a motor in.

A cable run to a wall switch is handled perfectly well by 2-conductor cable. The catch is that every wire to a wall switch must be considered as "hot" regardless of its color.

Grounding and ground-fault protection of outdoor receptacles is handled by GFCI devices.

The MC stands for "metallic-clad"; PVC is a plastic cable.

Overlapping metal tape wrap is allowed in the MC specification (article 334 of the NEC).

Corrugated metallic sheathing is allowed in the MC specification (article 334 of the NEC).

Smooth metallic sheathing is allowed in the MC specification (article 334 of the NEC).

MC cable has fewer restrictions on use, and also has a wider range in the number and size of enclosed conductors allowed.

"AC cable is limited to a maximum of four conductors plus ground; MC cable is unlimited in the number of conductors enclosed " is a valid description. Also, MC cable is allowed a wider range in the size of the conductor wires.

MC cable sheathing only supplements the internal ground wire and is not considered to participate actively in grounding.

The individual paper wrap is the most visually distinguishing difference between the two types of cabling.

Most circuit breakers function by means of an electromagnet that pulls electrical contacts apart.

The bimetallic strip is commonly used in a circuit breaker.

Metal melting interrupts a circuit quite effectively, but this is how a fuse operates, not a circuit breaker.

GFCI devices, rather than circuit breakers, operate by monitoring the level of current on both the hot wire and the neutral wire.

"A sudden surge of current energizes an electromagnet that pulls together electrical contacts and enables the flow of electricity" is not the correct answer. A circuit breaker does not enable, but shuts off the flow of electricity.

Preventing a surge of current from overheating wires and possibly causing a fire is the primary function of a circuit breaker.

Shutting the power off in a circuit in order to repair or replace a device safely is a handy function of a circuit breaker. When the device has been installed, you can then return the power to the circuit by making the appropriate change at the circuit breaker.

Turning off and on an array of lights should be handled by a simple switch, not a circuit breaker.

Opening and closing a circuit to an HVAC system in response to ambient temperature changes is what a thermostat is used for, not a circuit breaker.

Automatically turning outdoor lighting on at night and off during the day is the function of a photoelectric sensing switch, not a circuit breaker.

UPS stands for Uninterruptible Power Supply, and is used to provide power to devices that should not be shut down abruptly.

Very few UPS devices also incorporate a level of surge/spike protection, but in general these separate functions are handled by separate devices.

Some UPSs provide steady, "clean" power, but many do not. An in-line UPS provides some line conditioner functionality, but a stand-by UPS does not.

Many UPS devices can generate notifications and alerts, as can many computer operating systems. But this is not the primary function of a UPS.

The 110 punchdown block is by far the most widely used system for connecting LAN cables between patch panels and user outlets.

The 66 punchdown block is used mostly with telephone and Category 3 connections; although 66-style systems can be used for Category 5-based LANs, it is not as common.

The Bix punchdown system is rarely used or seen outside of Canada.

The Krone punchdown system is higher in price and requires its own tools, and is not the most common choice.

The formula is Watts = Volts X Amperes. At the standard "110" voltage, a 60-watt bulb pulls about half an amp to operate. It is customary and allowed to overload a circuit slightly (by 10% to 15%), since very rarely will all appliances drawing power from the circuit be on simultaneously.

A circuit breaker rated at 15 amps can handle much more than this load of 20 bulbs.

If all 40 bulbs were lit at the same time, the breaker would blow in short order. This is unlikely to happen, but the circuit would be considered as overloaded in design.

A circuit breaker rated at 15 amps can handle much more than this load of 10 bulbs.

The resistive type of touch screen uses two movable layers of flexible material over a glass plate, and these devices are the most sensitive to scratches and other damage.

The capacitive type of touch screen uses a conductive single layer of clear material applied directly to the glass, and is relatively durable.

Infrared touch screens throw two wide beams over a glass plate; there is nothing on the plate to be damaged. Moreover, the infrared emitters and sensors along the edges can be shrouded for protection.

In the SAW system, high-frequency sonic waves crisscross the screen, which is merely a durable glass plate. Also, the sonic emitters and sensors along the edges can be shrouded for protection.

The capacitive touch screen must be contacted by a conductive surface, such as a fingertip. This can be compensated for by the use of a conductive stylus.

Resistive touch screens register any pressure on two layers of conductive material and may be used with heavy gloves.

Infrared touch screens rely upon an object-any object-breaking the path of the infrared beams, and may be used with heavy gloves.

SAW touch screens rely upon an object-any object-breaking the path of the high-frequency sonic waves, and may be used with heavy gloves.

Many Web pads have no capacity to connect by means of a cable, but rely completely upon wireless technology, either on-board or by means of a PCMCIA card.

The most common type of physical port in a Web pad is USB, although COM ports and PCMCIA Type II are also available.

Email and Web browsing are the primary functions of a Web pad.

Although keyboards and a pointing device may be attached to a Web pad, some peripherals require that the Web pad be seated in a cradle with ports for these devices.

There is no need for high voltage current to be used in the transmission of keypad signals.

Low-voltage wiring is common when the keypad must be placed in a fixed location, such as near the entry as part of a home security system.

Infrared is short range, usually line-of-sight, and is commonly used for remote control keypads that signal to devices in the same room as the user, such as audio/video equipment.

Radio frequency signals are commonly used when the keypad must be completely mobile but within a short range of the controlled device. R/F is the choice when walls or doors can separate the keypad from its receiver, as in cordless phones and garage door openers.

The twists in the wires is paramount to keeping the carried signal contained within the pair, as the separate pulses each wire carries is synchronized with its pair partner. Together, the twisted wires cancel out inductance emissions outside their own space-IF the twist is maintained. Untwisting the wires to install an RJ-45 connector will undo this effect.

Properly installed UTP cabling will not interfere with nor be interfered with by other cables (including telephone/voice wiring).

The length of the run is a factor in attenuation of the signal, not in crosstalk.

Fluorescent lighting may be a source of EMI (Electromagnetic Interference) but not crosstalk inside the cable itself.