Lower-priced versions of computer systems that allow architects, draftsmen and interior designers to "draw" electronically eventually will find their way into the average home, a Rockville company says.

GTCO Corp. produces computer-aided-design systems (CAD) featuring an electronic tablet that permits creation of drawings five to 10 times faster than a draftsman working by hand, said Donald E. Carruth, the company's president. Drawings created with the system can be stored on computer discs or reproduced by standard computer pen plotters.

GTCO's Vector Sketch system features a sensitized drawing surface, or digitizer, over which a hand-calculator-sized "cursor" is moved. The cursor has up to 16 control buttons and a round glass window with a cross-hair. A wire grid under the surface of the digitizer tablet translates the cursor's movements into lines on a computer screen.

The cursor's buttons allow the operator to "draw" lines between two points, automatically reproduce basic shapes such as circles, squares and arches in any size, and create other configurations once and recall them later, speeding routine work. Errors drawn on a terminal screen can be corrected easier and faster than those set down on paper, according to Carruth.

Lines can be placed with extreme resolution and accuracy. The system includes a zoom function, permitting detailed work to be created at a larger size, then reduced to the drawing's actual scale.

Architects, draftsmen, interior designers, and universities teaching computer-aided design are among conventional buyers of Vector Sketch systems. But television stations also are using them to prepare charts, surgeons to plan operations and to compare anomalies, and various government agencies to analyze photographs.

Photographic analysis is performed by projecting a photo onto a special digitizer tablet and using the cursor to plot data. The system then can produce a digitized representation of the parts of the photo that the operator has traced.

Vector Sketch, with accompanying software, is the first system compatible with the IBM PC computer. Carruth said that Vector Sketch represents a significant price breakthrough at $7,500 to $8,000 for the system and an IBM PC compared with $50,000-plus for larger systems. The price range for Vector Sketch systems covers models with different kinds of cursors and with digitizer tablets ranging from 11-by-11 inches to 42-by-60 inches.

GTCO is a 7-year-old firm that was founded by Joe Fadden, the principal owner and chairman.

Carruth believes that Vector Automation Inc. of Cross Keys is the only other producer of CAD systems in the Washington-Baltimore area. Vector offers Cadmax II, a complete CAD system that starts at $53,800, and Graphicus 80, a three-dimensional graphics terminal that starts at $28,500. A drawing produced on a three-dimensional graphics system can show perspective and can be rotated to depict an object viewed from different angles.

About 10 companies make digitizers. Privately held GTCO is the second-largest independent producer of digitizers for sale rather than for internal use. It has three product lines: Vector Sketch systems, digitizers, and special-purpose graphic analysis systems. Two-thirds of GTCO's 125 employes work on the production lines. Sales were $4 million last year, and Carruth expects them to double this year.

"The day is going to come when every home will have its computer," and eventually CAD art systems will be found in homes, Carruth said. As part of the march toward this goal, GTCO is planning to introduce a complete line of lower-cost, lower-resolution CAD systems.

Carruth has been with GTCO for two years. He spent two years with M/A-COM of Rockville as vice president for finance and administration after 15 years with Western Union Spacecom.