There is a new epidemic sweeping the Washington area and it is evident in the change of conversation topics. No longer do we hear about the problems of the D.C. schools, grocery prices or real estate hikes.

Now the question is: "What kind of a system do you have?"

It all began innocently enough for me. I was pulling weeds in my backyard, when THE SOUND shattered the stillness and obliterated the gentle buzz of bumble bees. I looked up anxiously, thinking that perhaps an emergency ambulance had crashed through my neighbor's house.

"Don't worry," piped up the 9-year-old from next door. "The Smiths have probably tripped their alarm."

"Alarm? What alarm?" I questioned, wiping my earth-stained hands and trying to hear over the WOO WOOO WOOOO.

"They have a burglar alarm and they must have come in and forgot to turn it off."

I was mildly surprised to think that anyone in our modest single-family home neighborhood in Chevy Chase had installed a burglar alarm. They were necessary for the Rockefeller types on Foxhall Road. But us?

True, we had all been nervous during last year's Great Sterling Silver Robberies, but most of us took out $30-deposit boxes at the local bank. Good-bye silver except for holidays and important parties.

I shrugged off such thoughts and went back to my garden. Tales of homes burglarized, however, began to occupy neighborhood conversation.

My telephone would ring and Wendy, a good friend, would bring me up to date on the latest news:

"Five o'clock on a rainy night, we were all in the family room and didn't hear a thing."

"They got all of her porcelain figures and antiques."

"Second time around for the Jones family. Everything wiped out."

Prime time seemed to be around 4 o'clock in the afternoon, preferably on a rainy day. I stopped taking my daughter Gwyneth out at that time of day and decided that home activities would be fulfilling. I started turning on lights in the living room and kitchen if I had to leave. I read with great interest interviews and seminars conducted by burglars. They were making it big on the circuit and the newspapers were carrying their advice columns:

Keep lights on after dark, secure your basement and rear windows, leave a radio blaring while you are away. Close your curtains so no one can see if you have family silver on display. And, best of all, install a security alarm system.

I dismissed the last suggestion as impractical and unnecessary. Alarm systems were very expensive and anyway, we didn't want to live like that.

But?

Saturday morning, 9 o'clock. The phone rang. Wendy again.

"They got the Brown house yesterday afternoon."

We agreed it was awful. I got all the details and began to worry. They had used a crowbar on the kitchen door and just walked off with everything.

"This is it." she announced firmly. "We are going to do it!"

Do it? Do what?

"I'm getting estimates this week from a security firm. I've got to have some protection. Jim is away a lot and we just can't go on like this. Every time I go out I feel as if . . . "

Two weeks later, Wendy, beaming, showed me the intricate workings of a home burglar alarm system. Wires were well hidden under windows and around doors. A little digital box hung innocently in the foyer. An alarm horn, complete with strobe light was displayed prominently on the outside of the house.

I went home and brooded. I looked around at all the possible ways a burglar could get into the house. What would a burglar want to get in for, anyway? The black-and-white 11-inch TV with the broken antenna? The silver-plated tea service from Woodies? Gwyneth's dollhouse?

Then one day I returned to the house around 11 a.m., to see police swarming around. While I had been up in my study earlier, the house next door had been broken into by a burglar who had come around the front, hidden behind the bushes and broken into the basement window.

The neighborhood buzzed. Women gathered to compare notes.

Later that day I called a burglar-alarm company and arranged for a representative to come over and give me an estimate. I entered a world of new words that afternoon: tripping windows, impact sensors and diodes, strobe lights and timing mechanisms.

We walked through the house and suddenly the whole place seemed vulnerable. The tree near the kitchen window became a threat. Someone could climb and enter there. My lovely French door leading to our porch was suspect. What if some maniac slashed through the porch screens and smashed that door? It had to be double tripped! They might use a crowbar or smash through the glass.

Gwyneth's room and the back of the house were scrutinized. Visions of men, Dracula-like, crawling up the slanted porch roof to enter her bedroom raced through my mind. How about the chimney?

We agreed on terms, and Tom arrived the following week to start drilling throughout the house. Windows and doors were wired, an alarm box placed in the hall closet, code numbers decided on and programmed, and finally the big day arrived. He drilled through the front of the house and installed the alarm box and bell.

We tried out the alarm and the neighbors came running. We pounded on windows and doors and opened and shut them. Everything was in working order.

I plastered new decals all over the windows and doors. PROTECTED BY ELECTRICAL SECURITY SYSTEM. I looked up lovingly at the siren, sternly guarding my castle.

My neighbor, who had scorned the thought of an alarm, called Tom and he spent the following week installing her system.

We talked about the impact on our children. They were young, at an impressionable age. We didn't want them to be fearful, to imagine a world filled with dangerous criminals just outside our electronically wired front doors.

"Darling," I began, "what do you think of the alarm system?"

"Nothing much," she shrugged, "everybody's got one. We wouldn't want to be the only ones on the block without one. Amy likes hers a lot. When are you going to tell me the combination?"

That was all a few months ago. My life hasn't changed much since then. True, I'm no longer home every afternoon by 4 o'clock to protect the place and I've learned to live with and appreciate my security system.

I view it as a no-nonsense, protective friend who has come to live with us.

Little lights blink on and off to tell me that it is not set. Other lights inform me if the main entrance or any of the windows are open. When set, I have exactly 45 seconds to deactivate the siren or it will blast my ears off. I've informed all the neighbors about the alarm and tell them of my comings and goings. If it does go off, they will call the police. If there is an electrical power failure the whole system will transfer to a battery and continue to function.

If I lock the door and want to reenter the house I must deactivate the alarm. I'm always forgetting something, so it's not unusual for me to have to set the alarm twice before I pull the car from the garage. When I return, a buzzer warns me that I must use my combination to turn the system off.

Our quiet neighborhood has changed in the last few months. Crickets are frequently drowned out by THE SOUND.

A neighbor some blocks away can't seem to remember to deactivate the alarm in the morning, so WOO WOOO WOOOO has replaced my alarm clock as a wake-up call. A few weeks ago Wendy's alarm sounded for two hours before she got back to turn it off. A bird had flown into her rear sliding glass door and set the siren off on impact. Sirens go off at every hour of the day and night; people leaving for work in the morning or returning at 2 a.m. all seem to forget their guardian home security systems.

Sales of residential burglar alarms in the Washington area have almost tripled in the last five years, replacing, perhaps, the dishwasher as the top must-have item. In the past three months six have been installed on our side of the block alone, and there are more coming.

But this morning the phone rang. It was Wendy.

"Have you heard what happened yesterday?" she gasped.

"What? What?"

"They hit two houses."

"Did they have alarms on?"

"Yes, they had their systems on. The burglars didn't go inside. There were two men with a truck and a house ladder. They are going around the neighborhoods taking down the downspouts and gutters. COPPER IS WORTH A FORTUNE. They're just ripping it off the outside of houses and melting it down."