Farecard, that machine-dispensed, magnetically-encoded, wallet-sized ticket that is going to be the passport for Washington area citizens wishing to ride the subway, will go to work June 13.

Metro general manager Theodore Lutz told metro board members yesterday that Farecard dispensing machines and computerized subway gates will be put into operation that Monday on the present fare system - exact change in a human-monitored fare box - until the subway expands by 12 miles on July 1. Then, the Farecard collecting method will be the only choice systemwide.

Briefly, the Farecard is purchased in machines outside the entry gates to Metro stations for 40 cents to $20, depending on how much fare the customer wants. The card is inserted into a gate again, and the computer automatically deducts the value of the train ride from the value left in the card and permits the rider to leave the station. The card is returned by the machine, and the amount of fare left in the card is printed on the card's face.

The existing fare structure of 55 cents for a subway ride during rush hour and 40 cents the rest of the time will prevail until July 1, when a new fare struture based on distance traveled formula requires computers to collect, and that is the reason Farecard was chosen.