"Tom, I've heard of a machine that's going to put you out of business," the Marriott Corp. employe said.

Tom Bonacorda's Spartan Plumbing Co. of Bladensburg had been doing residential and commercial plumbing repairs for 18 years. When he got home, he asked his wife Patricia, "What'll I do?"

"I said we've got to find out about it," she recalled.

"We went to Texas, and we looked at it, and that was it."

"It" refers to the Longhorn Sewer Cleaner made by Automatic Sewer Systems Inc. of Austin, Tex. The automatic cleaning devices haven't put Spartan out of business, but now the Bonacordas have a second business, Aztec Construction Supply Co. Inc., that distributes the cleaners in 13 states along the Eastern Seaboard from Maine to Virginia and west to Pennsylvania.

Grease and other sewage present especially severe problems for restaurants, hospitals and food-processing facilities. The Longhorn consists of a flexible cable permanently installed in the main grease or sanitary line and connected to a heavy-duty motor that rotates the cable once a day for 90 seconds to scrape away material that has collected in the line.

Two models are designed for commercial lines of various lengths, and a third is for residential sewers. There also is a hand-operated floor drain cleaner.

Aztec and Longhorn claim that the permanently installed automatic cleaners will keep lines open when operated once daily, eliminating sewer-related plumbing calls. Aztec officials say the Longhorns are the only automatic cleaners on the market.

Verne D. Bossie of the Chesapeake Bay Seafood House said a Longhorn cleaner was installed in the Waldorf restaurant in June. "It's probably cut our plumbing bills--I would say between $200 to $300 a month," Bossie said, adding that the unit installed in Chesapeake's New Carrollton restaurant in October 1981 "already has paid for itself" in reduced plumbing bills.

An opposite reaction to the Longhorn comes from an official of Chart House Inc., which holds the franchises for some 380 Burger Kings and other restaurants in Houston, Louisiana, the Mississippi Gulf Coast, the Florida Panhandle and Virginia, including Fairfax.

The official--who did not want his name used--said that the Longhorn's flexible rod gets clogged because it has no teeth, necessitating maintenance, and that he doesn't want more installed in his restaurants.

"My biggest problem with it is buying a piece of very technical equipment for a problem that can be avoided" by properly training employes in preventive maintenance, he added.

In a letter to Automatic Sewer Systems dated June 1, 1981, however, another Chart House official praised the Longhorn units that had been installed up to then in Chart House restaurants.

"I am seriously considering the installation of your machines in all of our restaurants," the official said in the letter, a copy of which was included with promotional literature for the Longhorns.

And Longhorn President Chuck Breon, a former Houston plumber who invented the cleaner, admits that the rods can clog on occasion, but asserts that the cleaners still save money in the long run. "Even a Rolls Royce breaks down sometimes," he said.

George Bowley and Dynamic Systems Inc. of McLean have found something that they say gives an electric guitar a brighter sound.

Light.

Bowley, an engineer and guitarist, has replaced conventional guitar strings with optical fibers--thin glass strands that can carry light. A light source built into the headstock of the guitar transmits light through the optical fibers. When the guitarist fingers the strings and strums them, the resulting vibrations affect the light passing through the strings. A light-sensitive pickup at the guitar's bridge generates an electrical signal that is passed on to the amplifier.

Dynamic Systems says fiber optics eliminates instrument hum and noise present in standard electric guitars, offers improved frequency response and string wearability, and costs less. It also eliminates the possibility of a dangerous electrical shock that could occur if wiring were faulty and a performer touched both a standard electric guitar and a microphone connected to a different electrical ground system, for example.

The company, which was formed in 1977, generally performs engineering analyses and project planning, mostly for the Defense Department. It is involved in a Naval Research Laboratory fiber optics sensor systems program.

"We are actively working in the petroleum services area--using fiber optic sensors for geophysical exploration," said Robert E. Einzig, DSI's corporate director. He said the company also is talking about the potential use of fiber optics for medical diagnosis and treatment beyond their current use to help physicians see inside the body--to sense temperature, pressure and acoustics.

Meanwhile, DSI is awaiting approval of a patent application that covers its only fling into show business.