Behind a rickety plywood panel stands Danny Walsh. Before him are 188 switches connected by clumps of multicolored wire connected to 1,100 tons of bombs planted in mortars ready to blow over the Mall in a flash of light and thunder. But none of it will go anywhere if the Sears battery under the panel fails. $"For a big show we ought to have another battery, just in case," frets 75-year-old Felix Grucci, patriarch of the Grucci family, whose New York Pyrotechnic Co. sent shimmering fireworks across the sky last night in honor of the nation's 204th birthday.

But Danny Walsh, 28, a boyhood friend of Grucci's son (Felix Jr.) and an employe of the Gruccis, has tested the battery, and he steps to the keyboard and hits switch No. 1. It is 9:20 p.m.

Forty-six shells rise off the ground for a grand opening in exploding flashes and splashes of white, red, blue, green and gold. Walsh doesn't look up. He's listening to the timed, pre-recorded commands coming through his headset, and like an extension of the electrical machinery he pulls the switches on cue. "Fire one ready two," says the voice of the cassette at his feet. While above his head the kaleidoscopic aerial bombs are exploding and straight ahead, some 400,000 people are arching their necks back and ahhing in unison.

Supposedly, somewhere out there, music is playing, and for a second you can almost hear "Home on the Range." The timing of the switch-pulling was long ago coordinated to the tempo of the music. Walsh and Felix Jr. are just trying to see and to breathe through the acrid smoke rising out of the ground some 75 feet from the edge of the Reflecting Pool.

While Walsh handles the mechanical end, Felix Jr. and his assistant, Dave Wright, are doing the handwork: loading 40-pound shells wrapped in brown paper twisted at the end like giant Tootsie Rools into mortars, lighting them with a torch and sprinting off behind a brown van, known to them as "protection."

As flaming ash from the "chrysanthemums," umbrella shells and three-shell reports rain down on the ground. The beat now is established and the crowd is roaring to the erratic tempo of the explosions. The bombardment seems to have become normal when Grucci and Wright head over to the rows of shells curving along the pool that eventually will become the finale.

Then Grucci takes his flaming magenta torch to the lifeline fuse that carries the spark to the branching fuses, where it is consummated under a protective cover of paper penny and dime wrappers, courtesy of some bank. One spark lights its shell, then carries along to the next, sending swirling flame and shooting sparks in a 20-foot column along the curve in the line of mortars.

Grucci strolls 10 feet ahead of the wall of sparks carrying his torch in case the chain somehow breaks. Down the single row of shells. Then the sound, the smoke and the light double, as the flame branches into two rows of shells. Grucci quickens his pace. And the spark reaches a third row. The sky is white as the rockets shoot off into the night. The shimmering paper stars can barely be seen through the smoke. The pounding is beyond any rhythm; it's continuous.

But Grucci has stepped beyond the rows of the finale still in progress. He now is frantically waving the torch in a circle to signal to Wright, across the pool, to let rip the final shot. The Grucci Special.

A single light shoots out from the ground near the corner of the pool, rising; arching gracefully. It gently, silently bursts into a long, delicate rain of yellow lights crisscrossing the sky that eventually transforms into a twinkle of delicate white flaming stars falling lightly toward earth.

But 30 seconds before the Gruci Special ended, the men on the ground were grasping each others' forearms. Drenched in sweat, they cracked smiles and popped open Stroh's cans. Walsh, a bit jittery, says, "I almost lost it a few times there. Two of 'em didn't go. But two out of 2,000 ain't bad. You got your money's worth." Friends step slowly through the smoldering craters and tangled wire. And for the first time in at least 40 minutes, Dave Wright lights a cigarette.