A quarter century ago, deaf astronomer named Robert Weitbrecht conducted the first deaf-to-deaf telephone call by hooking a Teletype machine to a phone through a modem he invented. In 1969, 12 families in St. Louis set up a relay service to allow their deaf relatives to talk to businesses and other people.

The relay-service system remains the basic technology in use today by the deaf and hearing impaired. Recently, however, a new system was tested in the Washington area.

The new system, called Telecommunications Network for the Deaf (TND), allows deaf people to have longer and more private phone calls, without a third party present all the time. Bellcore, the research and engineering consortium of the seven regional Bell telephone companies, recently finished testing the new system, which enables the caller to place a call with less operator assistance and allows the operator to help more than one caller at a time.

Jim Tobias, a member of Bellcore's technical staff, said there are 22 million to 24 million Americans with hearing impairments -- 19 million are able to use the telephone with the help of hearing aids, and 3 million need the telecommunications device for the deaf (TDD) to communicate by telephone. The TDD is a machine similar to a typewriter and has a screen on which messages appear.

Tobias said that 300,000 deaf customers have TDDs, a number he said is small because the machines are costly -- $200 to $900, depending on its features -- and the lack of awareness of its availability.

Tobias added that Bellcore hopes that the 3 million people who would benefit from the TDD would be able to gain access to the machine.

Under the present system, for a deaf or hearing person to make a call, a customer first calls a relay station, and an operator dials the number of the person being called. The operator or the telephone interpreter then facilitates the conversation, relaying the message from one end of the line to the other.

The interpreter can either relay typed messages from one deaf person to another or listen to a hearing person's spoken words and type them into text that is electronically displayed on a deaf person's TDD. When the deaf person types a response, the operator receives the text and reads it back to the hearing person at the other end. Such calls are usually limited to 15 minutes.

Under the new TND system, automation takes over at certain points in the call. Instead of each word being displayed as it is typed, the operator becomes involved only after the whole text or message is typed. This allows the interpreter to attend to other calls. More than one operator may even take care of a single call, diminishing the likelihood that someone is listening in on an entire conversation.

Kris Beaman, 40, who has been deaf since she was 3, said she has enjoyed more private conversations using the new telephone network for the past five months.

"I know I don't spend so much time waiting at my phone to get through the busy signals that used to be normal with other relays," Beaman said. "And, I can make one call right after another for as long as I need to or desire, which is something I'm very grateful for."

The system has been tested in Virginia since last March by Bell Atlantic Corp. and the Chesapeake & Potomac Telephone Cos.

Initial testing of the TND system showed that it reduced delays and privacy problems by automating many relay operator functions -- such as call setup and billing -- and by having several operators translate different portions of each call.

Tobias said Bellcore wanted to develop the TND because it saw "early on where the regulatory and legislative thrust were going and we love to see opportunities where we can use technology to enhance the quality of life."

Elaine Elliott, supervisor and trial site coordinator, said Bellcore will soon be analyzing the past six months' data and building a larger test system while trying to develop a statewide system.

Bell Atlantic spokeswoman Tricia Rimo said that after evaluating the results, the company is "committed to explore other avenues." She declined to say what the company was working on but said that "something is in the works." The other Bell companies are also set to decide whether to proceed on full-scale development of TND.

Tobias said that development for communications equipment for the deaf has been advancing very slowly. "It's been pretty slow for all special needs," he said. "Specialized markets move more slowly."

However, during the last six to eight years, pressure for states to come up with better relay services has mounted.

Tobias said that although most states have some form of relay service for the deaf, only about 12 have mandated the service.

He added that about two dozen more states are on the "path of implementing relay services." Furthermore, the recently enacted Americans with Disabilities Act is expected to increase the number of such services in the country.

American Telephone & Telegraph Co. was the first company to provide relay services.

Now most of the regional companies and some nonprofit organizations provide the service.