It was a big occasion at the little museum when the man showed up who had been operating the radar on Oahu early that December morning when the Japanese came.
Joe Lockhart dropped in about two years ago. He had been the first to spy the planes on the screen; he thought they were a supply squadron. When he notified his superiors, they dismissed it as unimportant, and he went to breakfast.
Within an hour much of the U.S. Pacific Fleet was aflame or at the bottom of Pearl Harbor.
To jog Mr. Lockhart's memory of the events of that morning 50 years earlier, if such were necessary, there was a production model of the antennas that had first sensed the intruders 132 miles off shore and had tracked them all the way in. The model rises like a cybernetic tree above the small building that houses the Historical Electronics Museum, on West Nursery Road near Baltimore-Washington International Airport.
Inside is the same kind of equipment Mr. Lockhart was operating that day, the SCR 270 radar. There was the screen that, at 7:02 a.m., flashed the warning no one heeded.
The reason for that, according to Betsy Hall, the director of the museum, "is because radar was so new, people were unfamiliar with it."
Ms. Hall, 27, has a master's degree from the University of London in museum studies. She has been at the Museum of Historical Electronics for four years. "You meet so many interesting people," she said, referring to Mr. Lockhart.
The instrument before her, the first ground radar system ever deployed, was developed in the late 1930s. She flicked it on. The screen, until that instant the size and ivory-white color of an ostrich egg, displays a straight green line, then a blip above at 10 o'clock. It was receiving a signal transmitted from very nearby.
"It's elderly," she said, almost with a hint of tenderness, as if the machine could appreciate her concern. "It takes a while to warm up."
Briefly the SCR 270 is raised from the oblivion of its obsolescence. Then, click, the light is extinguished. There are other things to see.
There is a radio receiver, one of the first manufactured for commercial consumption, about 1918. It has a complicated panel of numbered dials, and a speaker that rises like one of Mickey Mouse's big black ears.
There is not much in the way of consumer electronics in this little museum, but they are getting more all the time, things like the television set from the 1940s.
The whole set is encased in mahogany veneer. It strives to resemble a piece of traditional furniture. Starkness in electronics design in those days was not fashionable; home appliances were created with soft, curving, convex lines, contrary to the Euclidean starkness that was to come, and that even today suggests up-to-dateness.
"A few weeks ago we got one of the very first microwave ovens," Mrs. Hall says. "Made in 1947, I believe."
It is huge but is not yet on display. Neither is the museum's antique fax machine. But eventually they will go into the museum, which has several galleries and a library of venerable technical manuals.
The old fax operates on a cylinder that, as it spins, reproduces each line of the message, one after another. This item was manufactured in the 1950s. It was very slow.
"The one we got would have taken an hour to send or receive a small document," Mrs. Hall said.
For reasons that are not entirely clear to Mrs. Hall, consumer electronics items of two or three decades ago are often difficult to find.
"It's kind of sad. There are so many big pieces of our history gone," she said. "What we have in here fits generally within a 50-year period."
Though not entirely. There is an array of earlier telegrapher's keys, vacuum tubes of every configuration, from the round and bulbous to the thin and streamlined. There are even specialized square tubes that look as if they were used in early Buck Rogers movies. There are, of course, radios from the second decade of the century, and Victrolas from the time of Edison.
But, Mrs. Hall points out, "The Victrolas are mechanical, not electronic."
So why are they in an electronics museum? She shrugs, a gesture that implies, Where else?
Robert L. Dwight founded the Historical Electronics Museum in 1973 and is its president. He is a retired defense worker for Westinghouse, a mechanical designer who "didn't want to see all this material scrapped by Uncle Sam."
He began the collection with an airborne radar system -- the AERO 13 -- manufactured in 1955. Today, he regards the 8-pound lunar TV camera -- a backup to the one the moon-bound astronauts took with them -- as the most valuable item, followed by the Pearl Harbor radar.
Generally, of those instruments among the museum's collection of about 8,000 artifacts, it is the older machines that are the more interesting, and those connected with war and defense.
The older machines refer to that epoch that experienced the first sudden advances in electronics, probably a time of greater invention than today, all the computer and microchip developments notwithstanding.
That was the period in the 19th century described by the communications philosopher Neil Postman in his book, "Technopoly," as the true "communications revolution." It produced "the photograph and telegraph (1830s), rotary-power printing (1840s), the typewriter (1860s), the trans-Atlantic cable (1866), the telephone (1876), motion pictures and wireless telegraphy (1895)."
As for war- or defense-related objects, the one with the most intriguing history is the Enigma cipher machine, developed by Dutchman Hugo Koch in the 1920s. It was used throughout World War II by the Nazi military forces, all their intelligence operatives and secret police.
It is a clunky apparatus; it looks like an early portable typewriter in a heavy wooden box, its steel casing covered with black crackly paint to diminish its metallic gleam. Mrs. Hall keeps it on a table in her office.
This was the most formidable cipher machine developed up to that time. It was thought by the Germans to be impenetrable owing to the number of coding possibilities it offered, what are described as its "statistical capability." They can be represented by the following number:
5,172,165,503,971,832,752,302, 775,832,450,732,675 (plus 51 zeros)
To crack this apparently uncrackable puzzle machine, Polish and French cryptanalysts developed the "bombe" -- a special computer. By 1938, as the Germans began their march across Europe, it had succeeded in penetrating Enigma's scheme. But in that year before the outbreak of the wider war, the Germans enhanced Enigma, raising its statistical capability even higher.
As the Nazis poured into Poland, the challenge of Enigma was taken up by the British. Using all the Polish and French data, they managed to produce their own "bombe" by 1940. This gave the Allies the key to German communications throughout the war and is thought to have been a major contributor to the ultimate Allied victory.
But in the end, it is the Poles who are credited with taking the mystery out of Enigma.