As signing for the deaf gains in public acceptance, sign language and finger codes are being taught increasingly to the non hearing-impaired, both as legitimate languages and as primary or supplemental means of communication for those with speech or language impairments.

By one estimate, more than 300 colleges across the country -- including George Washington University, Prince George's Community College and New York University -- now offer courses in signing. Each year, Gallaudet College trains at least 1,000 hearing people in sign language.

In reviewing job applicants, some airlines now credit training in American Sign Language (ASL) -- the chief manual system used by the deaf -- as a foreign language qualification. Harder to verify is the claim that sign (in its various forms) is the third most commonly spoken language in the country (after English and Spanish), used by about 16 million people.

And with the estimated 10 million nationwide impaired in speech (the production of articulate vocal sounds) or language (the appropriate use of words and grammar), exposure to signing -- often in conjunction with speech -- is increasingly a first rather than last recourse.

Public awareness, however, has apparently not kept pace with the still-controversial approach.

"My feeling is there's a lot of misunderstanding," says Betty Schopmeyer, supervisor of the Total Communication program at Christ Church Child Center, a private, nonsectarian school for multiply handicapped children in Montgomery County.

"When I tell people I teach sign language, it's hard for them to understand they the children she teaches are not deaf. They say, 'Why else would you teach them sign language?' "

Professionals who use signing with those affected by strokes, mental retardation, aphasia, autism, cerebral palsy or other ailments say the practice has generally not, as feared, further reduced the circle of people with whom impaired children and adults can communicate.

"We've been using some form of manual communication for the last 10 years," says Myra Barbour, director of the speech and hearing department at the Great Oaks Center, a state residential facility for the mentally retarded in Silver Spring.

"Previously there was some resistance to sign systems over speech from parents and others who assumed a person learning to use a manual code would not continue to make verbal attempts. On the contrary, it's been found that signing encourages more verbalizations . . ."

In most cases, that is. Some near-autistic children find signing confusing, says Sharon Murray, supervisor of speech-language pathology at the Children's Hearing and Speech Center of Children's Hospital National Medical Center.

But for many others, reported effects are dramatic.

Charles Diggs, speech pathologist and deputy executive director of the National Association for Hearing and Speech Action in Rockville, gives an example:

"I'm thinking of one particular boy aged 8 or 9. Previous work had been done with him for two or three years just to get him to be able to make the 'p' sound vocally. We switched to sign and in about three months he had a vocabulary of about 2,000 words, and not only sign words. Once he began to catch on to language concepts, he began to verbalize more as well."

Why do some children respond more quickly to signing? Some signed words, says Diggs, are more representational than their oral counterparts.

"Take the word 'tree.' There's nothing inherent in the sounds that make up the word to make you think of a tree. It's just something we have learned.

"Now take the sign for tree: You hold out your left hand parallel to the ground, palm up. The right hand is bent at the elbow resting on the left hand. Then you move the right hand as if the tree is moving in the wind, so that almost anyone can guess what it is. It's less abstract. It may be easier than verbal language to learn."

Plus, says Barbour, "signing is a gross motor movement, whereas speech is more of a fine motor movement . . . And it can be stabilized adapted to a slower pace for instructional purposes , where speech can't do that without distorting the word or its meaning."

Some groups, however, such as the Alexander Graham Bell Association for the Deaf in D.C., oppose the early teaching of sign to any young children, claiming it may interfere with the development of residual hearing and oral speech.

Controversy also dogs some gestural approaches with adults.

Use of the Amerind (American Indian) Code, for example -- a system of highly concrete, pictographic symbols adapted from ancient Indian hand talk -- has spread since its developer, 83-year-old Madge Skelly-Hakanson of Bratenahl, Ohio, reported success with stroke patients in the early 1970s. Some professionals, however, question the claimed results.

At the V.A. Hospital Center in Fort Howard, Md., at least 50 stroke patients, aged 40 and up, have been taught the code with varying success after losing their ability to use language. (The Amerind Code, lacking grammatical rules and tenses, is not generally considered a true language.)

Annamaria Basili, chief of audiology and speech pathology at the hospital, says one former patient, in his fifties and completely nonverbal, now uses his gestural fluency in hospital volunteer work.

"He communicates with people who do talk," says Basili. "He answers back with gestures. Most of the gestures he's using are very easy to understand, unlike ASL American Sign Language , where if you don't know finger spelling or the symbol for 'room,' let's say, you wouldn't know what it is someone was trying to communicate."

Skelly-Hakanson, former chief of speech pathology and audiology at the V.A. Hospital in St. Louis, also claims impressive results from the code with patients institutionalized as severely and profoundly mentally retarded.

"I took a population of 90 of these patients in St. Louis. Everybody who had worked with them had tried without success to teach them to talk and understand language."

Over the next three years, she says, "we got two-thirds of them to communicate at a fairly good level with Indian hand talk . . . It's a bombshell! I find lots of people won't believe this . . . They're antagonistic because it doesn't fit their ideas of what should be."

While Skelly-Hakanson claims the code opens communication with more people than ASL for the non deaf (because, she says, 80 percent of the code can be understood without training), ASL has the clear edge in most private and public institutions. ASL is better-known and more deeply entrenched even though it may be more difficult to learn.

"We have no clients using the Amerind code now," says Myra Barbour at the Great Oaks Center. "For us, we started out with our people learning ASL. We didn't want to reteach them. That's very difficult."

Schools generally favor ASL in combination with other "augmentative communication" methods.

Says Schopmeyer of Christ Church Child Center, "The big thing about the nonverbal hearing population is that no one system is going to be appropriate, adequate for all their needs. There has to be a combination of systems: sometimes signing, sometimes a computer with verbal capability, sometimes communication boards . . ."

The public school system has also had to add staff trained in sign and augmentative communication to serve increased numbers of speech and language-impaired children who have entered since 1978. That year, many such children were "mainstreamed" into the system after federal legislation entitled them to the best education in the least restricted environment.

The D.C. public schools use signing with a small percentage of their 3,160 students who are either mentally retarded or communicatively disordered.

"Almost all the teachers of severely and profoundly retarded are trained in sign," says Gail Houle, program specialist in the Office of Special Education. To meet increased demand, the school system has been offering free signing instruction to staff members for the last six years.

"It's one of the most popular in-service courses," says Houle, who notes about 60 staffers enrolled in a beginners' sign course last year.

In Fairfax County, at least 64 public-school children use signing -- most of them in a preschool program to facilitate the acquisition of language for impaired youngsters, according to Beatrice Cameron, assistant superintendent, student services and special education. In addition, she says, some of the public school system's estimated 300 children in multiply handicapped or mentally retarded programs use signing. Two Fairfax County public high schools offer sign language as an elective course for credit.

Montgomery County Public Schools count about 35 to 40 of their 4,952 communicatively disordered children who receive exposure to signing, according to Sally Veres, supervisor of the division of speech and language programs.

Six children with profound speech problems get special attention in the Total Communication class at the Lucy Barnsley Elementary School in Rockville. One of the first things they learn is sign language, to ease their frustration and assist them with academic studies in the hope they can ultimately move to regular academic classrooms.

But Veres acknowledges some parental complaints about the scope of this and other programs. "Part of the problem is that we've not been able to find enough qualified and trained individuals. We've been making a push for staff members to get more training in the field . . . We're in agreement no school system in the country has all the programs we want in augmentative communication . . ."