In the low light of the Emergency Medical Service headquarters in Maspeth, Queens, a score of uniformed technicians labor over the computer terminals that screen the city's 2,300 calls each day for emergency medical assistance.

Surrounded by banks of electronic equipment, the workers, emergency medical technicians, speak into their headsets and punch out data on computer consoles as they winnow through the calls to 911 - each conversation beginning with: ''Is the person breathing?''

For these technicians, known as call-receiving operators, and the dispatchers who maintain radio contact with the city's 269 ambulances, work routines have changed little in more than 10 years.

Meanwhile the hospitals and emergency rooms where the public ambulance service discharges its patients have gone from underused to overburdened - many of them no longer able to treat a patient load composed of sicker and sicker people. Computerized Data Bank

To address the crisis conditions in emergency rooms, the state's Health Commissioner, Dr. David Axlerod, introduced measures last week that Emergency Medical Service officials hope will allow them to cope better with a patient load that is expected to continue growing by about 6 percent each year.

The measures include a computerized data bank linking all of the city's hospitals with the Emergency Medical Service, providing dispatchers at headquarters and ambulance crews with up-to-the-minute information about hospital occupancy rates and the availability of beds in emergency rooms.

The state agency has also called for virtually all of the city's hospitals to participate in the 911 program. This was seen as a way to relieve overcrowding and to insure that all the hospitals in the city bear part of the burden of caring for the growing population of the working poor and uninsured.

Under current procedures, known as the diversion system, dispatchers continually work telephones at E.M.S. headquarters, ferreting data from all of the participating hospitals, then manually filling out charts to reflect emergency-room congestion.

When a hospital's psychiatric, medical or pediatric emergency room is too crowded to handle more patients, it is allowed - after independent inspection - to temporarily refuse additional patients arriving by ambulance. Diversion notices are relayed to ambulance crews who must decide where to take the sick. Relieving Suspicion

Emergency medical officials hope the new data bank will let them monitor minute-to-minute changes in emergency-room bed availability and tailor their instructions to ambulance crews with greater precision.

They also hope that it will relieve the climate of suspicion that prevails among participating hospitals, whose administrators often question why hospitals in a given area are allowed to divert patients while others are forced to continue accepting them.

''It'll make for better relations between us and the hospitals,'' said Edward Loss, a dispatcher who spoke between calls as he monitored emergency-room conditions. ''Each hospital would be able to see for itself who is diverting and for what reason.''

The new state measures include a request to the 15 hospitals that do not normally receive patients from public ambulances to participate in the emergency system. These hospitals, which range from small proprietary operations to large university medical centers, have not wanted to take the financial risk of accepting the ambulance patients. But if the hospitals do not join the emergency program voluntarily, state regulations could require them to take part. State 'Lit a Fire'

''The more hospitals I have to take patients to, the better things are for us,'' said Thomas B. Doyle, executive director of E.M.S. ''It's helpful in cutting down on the number of diversions, and it reduces travel time between hospitals.''

''At least seven hospitals have submitted applications to join the system in the last few days,'' said Dr. Alexander Kuehl, the retiring vice president of the city's Health and Hospitals Corporation for the emergency medical system. He credited the state with having ''lit a fire'' under the holdouts.

The emergency system's role in patient care begins with the fielding of calls relayed from the Police Department's 911 operators. As the demand on the system has increased, E.M.S. has broken patient classification into ever-finer groups based on medical priority. At peak times this allows the service to assure a 6-to-10-minute response time for those most in need.

In the operations room at E.M.S. headquarters, a voice filled with urgency occasionally surges out of the cacaphony of those fielding 911 calls.

''Somebody hit him in the head with a hammer?'' a paramedic shouts into his mouthpiece. ''The person is still breathing? He's bleeding badly?'' After quickly verifying the address forwarded electronically by the police, the paramedic tells the caller, ''Try to remain calm, ma'am, an ambulance will be there right away.'' System Called Ineffective

Once completed, this call, like all others, is assigned a priority, and the transcribed information is electronically relayed to a borough dispatcher who coordinates assignments for the 20 to 25 ambulances typically on duty in each borough at any given time.

With the current crowding in emergency rooms, many say the diversion system has become ineffective. When several of the hospitals in a given area go on diversion, as has been happening with increasing frequency, E.M.S. ends diversion status for everyone in the area. Under such conditions, overcrowded or not, hospitals must continue to receive ambulance patients.

''For years we have had a diversion system that has kept patients from going to places that weren't able to handle them,'' said Dr. Kuehl. ''But in the last year or so we have been virtually overwhelmed.''

The state's new computer system, by establishing a modern data base, could simplify decision-making in the field, Dr. Kuehl said. But with near-universal hospital overcrowding, and a reluctance to accept the growing influx of emergency patients, many of them poor, Dr. Kuehl cautioned, E.M.S. would have to continue independently monitoring bed availability through hospital visits. Otherwise, he added, ''it's sort of like having the fox guard the chicken coop.''

Photo of Nolmy Douglas and James Williams, technicians at the Emergency Medical Service headquarters in Maspeth, Queens, taking calls for medical assistance (NYT/Keith Meyers)