What would a deaf bank teller do if a pistol-packing bandit walked up to his window and shouted, "Hand over the cash!"?

"I'd look at him and just say, 'I don't understand you!'" joked William P. Middeleer Jr., one of the five Gallaudet College students who began work Monday as bank tellers at the new Riggs National Bank branch office in school's Ely Student Union complex.

The new office will serve the faculty, staff and 1,500 students of the nation's only liberal arts college for the deaf, at 7th Street and Florida Avenue NW.

Although some banks have installed TTY machines through which their deaf customers can communicate by typing, Robert Hileman, senior vice president in charge of the Riggs metropolitan division, said he knew of no other bank in the United States hiring deaf tellers.

With careers in banking all but closed to the deaf, many of whom are unable to speak intelligibly, the five Gallaudet students are breaking new career ground for the hearing-impaired.

American Banking Association spokesman Daniel Buser said, "There are a numbe of banks employing deaf and mute people in computer jobs and other positions . . . but they are not out on the teller lines . . . . "

While Gallaudet branch supervisor Gertrude Ghabel can hear, most transactions with the five deaf tellers will be communicated through sign language and lip-reading.

The five students were hired after a preliminary screening by Gallaudet's Office of Experimental Programs Off-Campus.

Middeleer, 27, was born with his hearing intact, but a high fever when he was 10 months old left him deaf. His father is a vice president of a Wall Street stock investment firm, and, since childhood, Middeleer has yearned for a job in the financial sector.

"Before I went to Gallaudet, one of my goals was to be in business administration," said Middeleer, spekaing in sign language while interpreters Francis X. Burton, 28, and Janet Bailey, 32, translated for a reporter.

"I had always wanted to follow in my father's footsteps [as a stockbroker]. He always told me 'You can do it,' but you have to do so much talking on the telephone that I'd always be frustrated. But maybe if I can get a secretary who could translate, I could do it," said Middleleer, encouraged by his break into banking.

"I'm happy to have had the chance to have the training and the opportunity to encourage others to follow us," Middeleer signed. "I hope that we will all be working permanently in banking so that the deaf can challenge the hearing . . ."

Middeleer, a native of Wilton, Conn., and Twila Turner, a 24-year-old Pennsylvanian, will work full time at the Gallaudet branch. Carol C. Caragliano, 24, of New York City, Stephaine Hamilton, 21, of Lexington, Ky., and Raphael H. Glower, 22, of Kensington, Md., will work part time, with their bank schedules tailored to fit their classes.

Riggs Staff Trainer Elaine Skelton, 26, and several other bank employes took a short course in sign language before the deaf teller class began May 11. But Riggs and Gallaudet officials found that the sign vocabulary had no sign for a whole list of banking terms such as "endorsement," "interest payment" aned "mortgage."

"We have given the university a glossary of banking terminology and it has been developing signs for some of these phrases or words for which no signs exist," said John Stacey, Riggs metropolitan division vice president for personnel operations.

Riggs also used the Gallaudet studens to test PLATO, a computerized teller training course developed by Control Data Corp., to the chagrin of some of the students, who were faced with learning Riggs' computerized account-balance system as well.

"The course [extended to four weeks for the deaf students] was too fast for me. I tend to get lost in the maze of information," said Glower, a philosophy major who speaks intelligibly and is only moderately hearing-impaired. "Sometimes, when I got home, I had to sit back and say, 'God, please let me understand it all.' It's so much to learn."

Of an estimated 206,000 persons with some type of hearing impairment in the metropolitan D.C. area, about 27,000 are totally deaf and could benefit from banks employing tellers proficient in sign language or other forms of deaf communication, said Brenda Rawlings of Gallaudet's demographic studies office. Nationwide, an estimated 14.5 million persons have hearing disabilities, close to 2 million of them living in total silence.

For Skelton, working with the Gallaudet students were enlightening.

"It's really made me focus on my communication with others," said Skelton, whose sign language name made up by her students means "smile." Working with hearing-impaired people, you have to be really expressive, which is something that I know now I wasn't in the past."

Riggs delayed opening the Gallaudet branch until summer, when most of the college's students are away, to give the new tellers a lighter customer load at first, said hileman.

The bank also is employing several Gallaudet students in its data processing department this summer, and will have a deaf clerical intern at one of its branches.

"We have talked to the people at the college about using this as a springboard to get hearing-impaired individuals on a banking career path," Stacey said. "It's a little hard to tell at arms' length what we can achieve. But this experience . . . will give us some measure of what we can do with the hearing-impaired in banking."