With wood, pegboard and wires, 15-year-old Daisy Carter built a miniature house. Through the nine windows, you can see if the light is on inside. But if you try to open the door, you'll be shocked.

The harmless electric shock -- and a siren -- might scare off Lilliputians. But Carter built her house to demonstrate a system for deterring life-sized criminals. And her DC1 Electronic Alarm System was convincing enough to earn her the grand prize at the 40th annual D.C. City-Wide Science Fair.

The prize will take the Northeast Washington resident to Fort Worth in May for the International Fair -- and, if she chooses, to the University of the District of Columbia on a four-year scholarship in 1988. Carter is finishing 10th grade at Woodrow Wilson High School.

It was Carter's older brother, Reginald Jones, who sparked her curiosity about electricity. "I became interested because he was always taking apart TVs and radios and putting them back together," she said.

"So we were talking about my science fair project, and it just popped into my head. 'Hey, could I build an electronic alarm system?' " Her brother helped her find reference books and choose materials.

"Sometimes, in the middle of making it, I would think, 'I'm not going to understand this. I'm not going to be able to do this,' " Carter said. "There were lots of times when I thought that I was going to give up and find something easy.

"But my mother, my brother and my church family all gave me a lot of support. And, of course, there was my school support," she said.

Carter's project included the technical drawings of the DC1, showing the paths of the electricity and the intricate wiring.

Carter hopes some day to patent and sell the DC1, which operates with a constant electric current in the wiring. When a window is broken or a door forced, one of the house's metal sensors picks up the disturbance, breaks the circuit, activates a siren and turns on the lights in the house.

The model house has a siren and one light bulb inside. It also has a doorknob that buzzes when touched. "This was the most fun. If you just slightly turn it, you'll get a shock," Carter said, explaining that she created the mild shock with batteries and a transformer. On a real house, the owner would turn off the system with a key.

The fair was held last month at Woodson High School. "What surprised me was that I was the only female entry of the 55 engineering projects in the senior high division," Carter said.

On the day of the awards, "I got up at 6, paced the floors, prayed at home, called friends and made sure I ate a good breakfast," she said.

Carter shared grand prize honors with Dunstan McMillen of Bethesda, a 10th grade student at Gonzaga, who entered a study titled "Jet Nozzle Effectiveness."

Carter also won awards from the Army, the Air Force, Minority Women in Science, the Junior Engineering Technical Society and Graduate Women in Science.

"I'm just elated that she was chosen," said Carter's teacher, Glenda Holmes. "She's worked very hard, and she is deserving of all the awards." Carter said she hopes to be an engineer and to have "a family, a nice house, and a big front and back yard."

Carter said she hopes that some day her family and others can have a DC1 system in their homes.

In her fair display, she wrote: "I wanted to make my very own alarm system that may one day be used throughout the city as a way of protection from thieves and crooks who seek to steal from those who may have worked so hard to get the things that they own."