DEAR TIM: My neighbor's house was struck by lightning. Fortunately, it did not cause a fire. However, the lightning apparently ruined their computer, phone answering machine, and many other electronic devices. Why didn't their house catch on fire and what, if anything, can be done to prevent my electronic devices from being destroyed? P. F.

DEAR P. F.: Your neighbor was very lucky. Lightning strikes generate temperatures close to 50,000 degrees F. The most likely reason a fire did not start was due to the fact that the duration of the strike lasted only a few thousandths of a second. This type of lightning strike is commonly referred to as a "cold bolt." It is also possible that they have an excellent exterior lightning protection system in place.

Electronic devices such as computers, VCR's, televisions, modems, etc. can be ruined or "short circuited" by relatively small current surges. Because lightning can produce enormous voltage surges, special measures should be undertaken in an attempt to protect this equipment.

Lightning can create havoc in your home even if it does not strike the house directly. The lightning can strike a power line that feeds your house. Telephone lines and power lines can experience voltage surges simply from the electromagnetic energy created by a nearby direct strike.

The first line of defense is to have an excellent grounding system with respect to all electrical outlets. The reason is simple. The voltage surge in the power lines will, in many cases, quickly "bleed off" to the grounding system. This is especially true if the grounding system has a very low resistance. This low resistance means that the electricity will travel extremely rapidly through it into the ground or soil surrounding your home.

However, different types of soil have varying capabilities to dissipate electricity quickly. Generally, moist sticky clay soils tend to dissipate electricity rapidly. Sandy, or rocky soils often dissipate this energy more slowly. Soil types can vary greatly in short distances, so you must be sure of the type you have. If you live in an area with very little or no soil, you have to install specialized grounding systems.

Most houses have only one grounding rod attached to their electrical system. The ability of your electrical grounding system to quickly dissipate voltage surges increases dramatically if you install numerous grounding rods. These rods should be spaced at least ten feet from one another in a series. The solid copper wire connecting these rods should be continuous and welded to these rods if at all possible. A mechanical connection, such as a clamp, is the weak link in a grounding system.

A secondary line of defense is to install a secondary lightning arrester inside of your electrical panel. Some of these arresters can withstand 15,000 amp surges. These products capture voltage surges on the "hot" 120 volt power lines feeding your house. These surges are then directed to the grounding system we just spoke of. These items should not be installed by an amateur, due to the fact that you are working with dangerous house current when installing these devices.

The final line of defense consists of transient voltage surge protection devices. These are the most common surge protectors on the market. They are available at electric supply houses and stores that sell electronic devices. There are many different varieties of this type of device. Some even protect telephone lines and electrical outlets at the same time. Remember, all three systems must be employed in order to provide the highest level of protection to your sensitive electronic devices.