Jack Gannon used to go to the hardware store carrying a notebook and sharp pencil so he could scribble notes to salesclerks asking the size, location and price of items he needed. Now Gannon shops from his home and in a few minutes orders nails, lumber, paint and plumbing supplies.

Gannon's shopping has become easier since an increasing number of stores started installing TDD machines that allow deaf people like himself to communicate with stores, government agencies and friends.

From their homes or offices the deaf can now order groceries, clothing, airline and railroad tickets and even car mufflers from dozens of local businesses that also have TDD machines.

TDD, telecommunications device for the deaf, is the general term for machines that resemble typewriters and are connected to a telephone receiver. The older models are called teletypewriters (TTYs). The caller and the receiver type their messages, which are transmitted through the telephone line. Each deaf person who owns a TTY or a TDD can communicate directly with department stores, insurance agencies, doctors, dentists, lawyers and other firms in the District that have installed TDDs in the past five years.

"I really appreciate it as a deaf person," said Gannon, director of alumni relations at Gallaudet College, the world's only accredited liberal arts college for deaf students. "Now I don't have to drive over to the store every time I have a question on a sale or need to know if something is in stock," he said.

While business use of TDDs is fairly recent, the emergency police and fire department, plus schools, the mayor's office and major utilities, have had TDDs for the past decade or more. Federal law requires that most public agencies have TDDs available, and Metro and Amtrak are required to have TDDs for making reservations. Metro is considering installing TDDs at pay telephones at three subway stations.

The District police special emergency number for the deaf that is connected to a TDD receives five to six calls a week.

Most District hospitals have TDDs, usually one in the emergency room or admissions office. George Washington University Hospital and Children's Hospital allow deaf patients to have portable TDDs in their rooms.

Stores as diverse as Sears, J.C. Penney, Midas Muffler, Giant Food and Hechinger's now have TDD machines. Each machine costs from $300 to $500.

"Businesses want to tap the deaf market," said Muriel Strassler, the director of public information for the National Association of the Deaf, which has headquarters in Silver Spring. Strassler is deaf.

The number of TDDs in District businesses is growing "at a fairly good pace as people become more familiar with them," she added.

There are an estimated 10,000 to 15,000 TDDs in use in the Washington area, according to a survey of companies that sell the equipment. An estimated 103,000 people in the area have significant hearing loss. About 24,500 live in the District.

The major local directory of TDD numbers lists 250 businesses in the Washington area with the machines, about 30 of those in the District.

Potomac Electric Power Co., Chesapeake and Potomac Telephone Co. and the Washington Gas Light Co., the city's three public utilities, have provided TDD services to the deaf since the mid-1970s.

Pepco and C&P receive large numbers of calls -- more than 10,000 a year -- because they offer a third-party calling service for the deaf. Deaf people can call one of the utilities and ask the company to call a business, a doctor or office that is not equipped with a TDD. The utility makes the call, then relays the information back to the deaf person.

Among businesses, Sears' catalogue ordering service gets about 25 calls a week. Giant Food's TDD line averages five to 10 calls weekly, for orders at any of the chain's 132 stores. The Washington Post has three TDD lines to facilitate classified ad and subscription services.

Hechinger's store at the Hechinger Mall in Northeast installed a TDD in late December and averages six calls a day. The number of calls will be monitored to determine if the machines should be placed in other branches, said store manager Hudie Fleming.

But Hecht's department store found its TDD line seldom used and discontinued the number last year because "there were virtually no calls," said Frank Shannon, Hecht's division vice president.

"If you find someone who would have a need for our equipment, we would probably donate it," he said.

Doctors, dentists and lawyers report light TDD usage, but many deaf persons complain that too few of these professionals have the machines.

"Some group health insurance companies now have TDDs, so it is easier to reach my doctors," said Marla Hatrak, who is deaf and the manager of special services for the U.S. Senate. She recently spent three days trying to find a lawyer because of delays in getting through via an interpreter.

As TDD usage increases, merchants with TDDs admit they are still learning how the machines work.

"It's really enlightening to see all these calls come in," said Fleming of Hechinger's. "A lot of people are just phoning to tell us they're glad we've put a TDD in."