A new type of housing that older Americans warm to

''We had to give away our washing machine, our dryer, our refrigerator, and our air conditioner.''

Dorothy Mulvey, a short, white-haired woman in a brightly striped jersey, might be telling the typical tale of a displaced elderly couple. During their working years, she and her husband lived in a large, four-room apartment in what is known locally as a ''three decker'' house. But they found their neighborhood deteriorating - and felt increasingly unsafe. Finally they moved.

Unhappily? On the contrary. As the couple shows off their new apartment - small shiny kitchen, large walk-in closet, two comfortable rooms - they are fairly chirping.

And as they point to features that make this more than a typical apartment - the call button, the signal light in the hall above their outside door, the lobby camera that allows them to monitor visitors on their own television screen - they are clearly comforted.

They are among the 94 tenants of Farnsworth House, a nonprofit ''congregate housing'' facility officially opening Wednesday in Boston's Jamaica Plain - built with private initiative, federal funds, and Yankee ingenuity.

The modern brick-and-glass facility, in fact, is evidence of a slowly evolving change in America's concept of caring for its increasing numbers of elderly. It is not an ''old-folks home'' of the sort popular in the 1930s. But neither is it a nursing home.

Instead, it combines self-contained units with social services available on request from more than 100 agencies in the neighborhood - ranging from homemaking to mental health counseling.

The goal: to serve elderly individuals and couples who, although described as ''frail,'' are capable of living independently.

''No one wants to over-serve anyone,'' says Deborah A. Robbins. As a vice-president of the State Street Bank and Trust, she administers a trust fund established by Charles H. Farnsworth in 1930. Mr. Farnsworth, who founded the First National Stores chain, left $1 million to establish ''a comfortable home for aged men and women . . . who have fallen into want.''

But his last heir lived until 1978, when the fund had grown to nearly $6 million. And the kind of home he had in mind (with 25 bedrooms, a common dining room, and ''a large living room with good-sized fireplace'') no longer answered the needs of the aged.

So the bank, with the advice of a committee of specialists, approached the state's attorney general and Supreme Judicial Court with suggestions for changing the will. The proposal called for a ''shared resources'' home - using seed money from the trust and public financing for the actual construction.

And, rather than using the entire trust to run the home (as Farnsworth had stipulated), they requested the funds be used to assist other nonprofit agencies and institutions serving the elderly in the Boston area.

The court, recognizing the impracticability of the original trust, agreed. The result: a piece of creative financing allowing the trust to both have its cake and eat it - to initiate the building project (ultimately funded by a $4.2 million, 35-year mortgage from the US Department of Housing and Urban Development) and to provide for the care of the tenants (who, under federal rental subsidies, pay no more than 30 percent of their income for rent).

''Essentially the entire trust has been preserved intact,'' says Ms. Robbins, who notes that the trust is now in a position to sponsor other similar facilities.

The trust, however, did put in funds to build a community dining hall and kitchen. Weekdays it serves 75-cent hot lunches to about 100 local senior citizens. Housing manager Marita Terefenko describes the dining room as ''an interface between the community and the residents.'' Its value, she adds, has been immediate: some Farnsworth House residents who had been house-bound for years in third-floor walk-up apartments now come down to lunch.

With gathering places on each floor - and with a fenced lawn, terrace, library, and rooms for washing machines and for social-service counseling - the building provides plenty of common space.

Which suits the Mulveys. ''Do you get in each other's way?'' they are asked.

''No!'' chuckles Mr. Mulvey, a spry man in a red corduroy shirt. ''I don't dare.''