In a Jerusalem hotel some years ago I was feeling particularly smug that I'd had the foresight to buy an adapter so I could plug in the heat disinfecting unit for my contact lenses.

My pride, however, turned to horror the next morning when I discovered my lenses had been charred.Other travelers report similar nightmares - computers that remain blank, hair dryers that smoke, electric toothbrushes that whir at extraordinary speed.

Considering all the potential pitfalls with electrical appliances abroad, it's no wonder some travelers steer clear of the issue entirely and either do without, or depend on hotels to supply hair dryers and irons.

But many smaller inns and hotels do not stock small appliances.

Moreover, many travelers prefer to carry their own appliances, particularly when they relate to personal hygiene.

Such appliances range from curling irons to plaque-removing toothbrushes to hand-held shavers and electric denture cleaners.

To use these appliances abroad requires some knowledge of electricity and, more important, the right plugs and voltage converters.

Basically, the problem of using electrical appliances abroad can be reduced to three areas:

First, plugging in the appliance. Because the configurations of wall receptacles differ around the world, you may have to use an adapter.

The second concern is voltage - the pressure under which current flows through an electrical system. Because most U.S. appliances are designed to work at around 110 volts and because many power companies abroad generate electricity at 220 volts or greater, you need a device called a voltage converter to step down the current.

Finally, there is the issue of how many times per second the alternating current in an electrical system changes direction.

In the United States, AC current changes direction 60 times a second - thus the phrase 60-cycle service.

But in other parts of the world, Europe being the best example, the current changes direction only 50 times a second.

And in some countries, like India, the current is direct, which means it does not alternate at all.

While the slower, 50-cycle service is generally not a problem for small gadgetry, like a portable clothes steamer, a lot of electronic equipment, like laptop computers and video recorders, work only on 60 cycles and can be damaged if supplied with a different current.

Fortunately, the equipment required to operate most small appliances safely is inexpensive, light and easy to use. Most luggage retailers, travel shops and department stores carry adapter-plug kits.

The opening on one side of the adapter is designed to accept the familiar rectangular, two-pronged plug found on most U.S. appliances. The other side has a different set of prongs designed to fit into a foreign wall outlet, assuming the voltage is 110.

While wall-outlet openings are configured in dozens of ways around the world, five configurations account for 95 percent of the outlets.

The two-pronged U.S. system, for instance, is also used in Central America, the Caribbean, South America and Japan. American travelers really need to carry only four adapter plugs: the plug that fits into the two round holes in continental Europe, the plug for Australia's two rectangular holes (unlike the American system, in which the openings are parallel, the openings in an Australian wall outlet form a "V"), the three-pronged plug for British bathrooms and the plug with two oversized round prongs for other British outlets.

All this assumes, of course, that electricity is being supplied at around 110 volts, which in my case was not true.

Although I was able to plug in my heating unit for the contact lenses, the unit got 220 volts of electricity, not 110.

While most of North and South America, the Caribbean and Japan have 110-volt electrical circuits, almost all European utilities generate 220-volt electricity. Elsewhere, voltage can run as high as 260 volts.

If you use an adapter plug without reducing the voltage, you are likely to smell a faint odor. It could be your appliance burning out.

"If you are in a high-voltage country, you need to protect that appliance from that high voltage," said Edward Crawford, the marketing director for Norelco's travel products.

"You need something to step down the voltage."

Unless your appliance can work on 110 volts and 220 volts - some hair dryers and electric razors, for instance, have switches that allow the device to work on both - you will need a separate voltage converter.

A cigarette-pack-size device also sold in most travel shops and department stores, the converter relies on current-resisting coils to step down voltage to 110 volts. Many converters are sold with a set of adapter plugs.

The one complicating factor is that there are two different types of voltage converters: one for appliances that consume a lot of power (hair dryers, irons and coffee makers), the other for low-power appliances like radios and shavers.

The rough cut-off point is 50 watts. If an appliance consumes more than 50 watts, it is considered a high-power device; fewer than 50 watts, low power. You can either buy separate converters or an all-in-one unit with a toggle switch.

"A combined unit gives you a lot of flexibility," said Donald Schubert of the Savvy Traveler, a travel-products retailer in Chicago.

For most pleasure travelers, the story ends there. Business travelers, however, need to know more.

Some electronic equipment like computers cannot tolerate 50-cycle electricity. Even if you use the proper adapter plug and voltage converter, you could still end up overheating and permanently damaging your computer.

The only way to know for sure is to check the owner's manual or to consult the manufacturer. In addition to an adapter plug and a converter, you may have to take along a transformer that allows 60-cycle electronics to work with 50-cycle current.

Although more than a dozen companies compete in the field, the business of adapter plugs and voltage converters is dominated by three players - Franzus, Remington and Norelco.

Although all three take a similar approach to electricity abroad (you insert your domestic appliance into a voltage converter, which in turn goes into an adapter plug that is inserted into a wall outlet), their products differ slightly.

Norelco, High Ridge Park, Post Office Box 10166, Stamford, Conn. 06904; (203) 329-2400, offers two travel kits. Kit 1 (suggested retail price: $28) comes with five adapter plugs that will work in most destinations and a voltage converter for high-wattage appliances like a hair dryer.

Kit 2 ($38) also includes a voltage converter for low-wattage devices like portable radios. The high-wattage and low-wattage converters are also sold separately for $18 and $14, respectively.

Norelco also sells a set of adapter plugs without the voltage converter - five for $10.

Franzus, Murtha Industrial Park, Post Office Box 142, Beacon Falls, Conn. 06403; (203) 723-6664, produces the same five plugs as Norelco but packages them differently.

You can buy four plugs in a packet - one each for South America, Europe, Australia and Britain - for $10.99. The plugs can also be bought separately for $3.49.

Franzus's high-wattage voltage converter retails for $18.49, its low-wattage converter for $14.99, and a combination converter that works with low- and high-wattage appliances sells for $29.49. Franzus also sells various kits that combine adapter plugs with a voltage converter.

Remington, 60 Main Street, Bridgeport, Conn. 06602; (203) 367-4400, sells only one product - a kit that combines five adapter plugs with a voltage converter good for appliances rated 50 to 1,600 watts.

One interesting aspect of the Remington converter is that it has a replaceable fuse; other units have to be scrapped if the electricity abroad somehow causes them to overheat. The Remington kit carries a retail price of $14.99.

The U.S. Department of Commerce has a helpful pamphlet, "Electric Current Aboard," that was last issued in 1984. It is scheduled for reissue, but no allocation has been made. The booklet shows which type of plugs are used by different countries and also gives type and frequency of current, number of phases and nominal voltage and tells if the frequency is stable enough for an electric clock.

Tom C. Witherspoon of the office of publications of the Department of Commerce said that the booklet was out of print but that reissuing it was planned.