Dennis Anderson slid a $1 bill into a farecard vending machine at the newly opened Rosslyn subway station yesterday.The machine quickly coughed up an 80-cent farecard and 15 cents in change. It refused to return his other nickel.

A few minutes later, Janet Dixon dropped 50 cents into another farecard vending box at the Rosslyn station. The machine gave back 25 cents and kept her other quarter. A red, "Out of Service" sign lit up.

Electronic technology hit more than a few snfus yesterday, as thousands of occasionally bewildered passengers confronted Metro's new multimillion dollar machines on opening day of the subway system's Blue Line linking suburban Virginia with downtown Washington. The electromagnetic, $53 million fare collecting system known as farecard appeared to be the clearest point of confrontation between man and machine. Farecard machines got jammed with wrinkled $1 bills. Malfunctioning farecard exits refused to open to let subway riders out. Long lines formed as prospective passengers waited to buy farecards that would let them in. Some riders marveled: some waited patiently; others got angry.

The farecard contraptions, moreover, were not the only sticking points in the newly enlarged Metro system.

Subway trains were repeatedly delayed during the day because of sticking doors and sicking brakes. The sticking doors were attributed by Metro officials largely to overcrowding. According to preliminary reports, a Metro spokesman said, the longest delay was 20 to 30 minutes.

On the platforms of stations along Metro's Blue Line, other apparatus also went on the blink. Escalators broke down at stations including Capitol South and Eastern Market. Elevators for the handicapped appeared not to be in operation at several stops. Pay telephones were marked out of service. Signs were still being hung. Lights beside the track at at least one station refused to blink to alert passengers to arriving trains.

On the whole, Metro officials characterized yesterday's mishaps and mixups as relatively minor and forecast that even their farecard troubles would quickly dwindle.

"The bugs are being worked out in the machines - as well as the bugs in the people," said Metro spokesman Cody Pfanstiehl. He attributed yesterday's snafus to public confusion as much as technological failings.

The farecard gadgets, manufactured by the Cubic Corp., are complicated, labor-saving, electromagnetic devices schedule based on the distance a pasway fares under Metro's new fare designed to compute and collect subsenger travels. The farecards themselves are wallet-sized magnetically encoded cards - a replacement for coins, transfers and tokens.

When a subway passenger inserts money into a farecard vending machine, an electronic scanner examines the bills or coins to make sure they are legitimate. Then the machine electronically encodes the value of the currency on the card's magnetic strip prints its value on the card's face and returns the passenger's change.

When the subway rider slides his farecard into the entrance gate, another electronic device reads the card's magnetic strip to make sure that the card is valid and that its value is at least 25 cents, a largely arbitrary figure. Then another device encodes the card to note the station and time of day at which the passenger entered .

When the subway rider gets off at another station and puts his card into an exit gate, another electromagnetic device reads the card's magnetic strip to check the card's value and the station where the passenger boarded the subway. Then a gadget, about the size of a postage stamp, computes the fare. A third electromagnetic device encodes the card again, deducting the cost of the passenger's ride from the previous value of his farecard.

With so complex a system, much can apparently go wrong as passengers learned and demonstrated repeatedly yesterday.

Anderson, the engineering consultant who lost a nickel in one of the farecard vending machines at the Rosslyn station, was reimbursed after a technician unlocked the machine. The farecard vendor had short-changed Anderson, the technician said, because what he described as a "fat nickel" got caught in the machine's works.

Dixon, the medical secretary whose quarter was gobbled up by another farecard vending box at the Rosslyn station, received a farecard after another technician came to help out. His explanation was that the quarter had gotten stuck because it was slighly bent.Dixon expressed annoyance at being delayed on the way to a doctor's appointment.

The Rosslyn station was among those hardest hit by malfunctioning farecard vending machines. At one point, five of the station's 10 farecard vending boxes were temporarily out of commission.

A range of factors - some solvable, some not - are said to have contributed to Metro-s farecard troubles. Many of yesterday's delay for passengers seeking to buy farecards or walk through farecard gates were blamed by Metro officials on confusion over how to use the machines. Passengers again and again tried to insert $1 bills and the farecards themselves into incorrect slots, often upside down or backward. Experience in riding the subway system will largely solve this problem, Metro officials said.

Delays at the farecard machines may also be reduced. Metro Officials noted, when additional machines are installed. Metro now has slightly more than 380 machines. according to Paul C. Johnson, a Metro design technician. By October, Johnson said, the number of vending boxes at Metro stations should climb to 659.

Apparently beyond solution, however, is the chronic refusal of the farecard machines to accept ragged $1 bills or wrinkled farecards. These often jam the machines, causing delays for riders. Metro and Cubic Corp. officials say no reliable scanning device exists that can contend with torn or crumpled bills and card.

Between the remediable and the irremediable are other farecard failings, described by some officials as initial lapses in a newly opened system. Some of yesterday's farecard troubles were attributed to the newness of the machines, many of which were installed this week and had not undergone a thorough shakedown.

Yesterday, a series of impromptu solutions were put into operations by Metro officials in an attempt to lessen the public's farecard headaches.

At stations like Rhode Island Avenue and Rosslyn, Metro officials - including Theodore C. Lutz, the transit agency's general manager - resorted to peddling $1 farecards to help handle long lines at the machines.

One resourceful station attendant, James Graham, started handing out free subway passes to passengers who wanted to ride the rail system at 7 a.m. yesterday at the L'Enfant Plaza station. Through a mixup, none of the station's farecard vending machines had been stocked with cards or change.

Metro's farecard troubles took many shapes yesterday. A repairman termed them "infant mortality."

Ralph McTighe, visiting here from Wilmington, Del., complained that a farecard bottleneck at the Dupont Circle station forced him to miss his Metroliner ride to New York.

At one point, machine jams at the Crystal City stop left about 130 would-be passengers waiting in line. One woman found that a farecard she bought previously had been eraded by a magnetic device that opens the garage door at her home.

Despite such mishaps, most riders appeared to take the expanded Metro system yesterday with eagerness, patience and some delight.

Even a blind woman who ventured onto the subway at Rosslyn mastered the farecard technique. Seville Allen, a blind employee of the Equal Employment Opportunity Commission, discovered she could slide her farecard into the entrance gate rightside up by feeling the card's magnetic strip with her fingertips.