* * * * * Her voice paused briefly, took a new tone, but was still covered by the whinings. "Miss Carlson, this is Ed Bronson. I cannot hear you clearly because of much interference. If you can hear me, make a lilting rill with your voice. This I can distinguish among the many stable-toned notes that are coming in at the time." The voice rilled up and down several times. Then there was considerable speech which Bronson could not understand. The upshot of this, however, was a gradual shutting down of the hootings and honkings until the receiver was clear. Then her voice came through again. "Mr. Bronson. I have requested silence for one minute. Where are you?" "Thirteen forty-eight Vermont Street, Central City Eleven." "That is across the street," she said. "Perhaps," he answered. "Well, it is," she said. "Unless we're in different Central Cities." "Central City, New Mexico, eighteen miles from Albuquerque?" "That's it. But we have little time, really, because we didn't get the clear as soon as we asked for it. They hung over a bit--the commercials, I mean." "Commercials?" he asked. Dumfounded, he began to wonder. Commercial, in radio parlance, meant any transmitter on the air for commercial purpose and the presupposition that this system of communications must be quite well known. How then had Ed Bronson, an electronics engineer, managed to live through the commercialization of an entirely new field of communications? "The commercial laboratories," she said. "Oh? Then this is a laboratory experiment?" "More than that--" Bronson heard with dismay the first thin whistle resume. He interrupted. "Miss Carlson," he pleaded quickly, "we're going to be cut off again. Meet me on the corner of Vermont and Thirteenth, please?" "Yes but--" That was all. The keening, piping howl came with ear-shattering loudness once more. Bronson turned off his gear and headed for the corner of Vermont and 13th. Let 'em hoot and howl. He'd speak to the girl in person! An hour later, Ed Bronson still stood there, leaning disconsolately against a lamp post in the bright daylight. A ring of cigarette butts surrounded his feet. Whatever it was it was important and he, Bronson, had the key. All he had to do was to find the door! * * * * * Bronson returned home. The trouble--one of them, anyway--was that his amplifier was a high fidelity affair, capable of flat transmission of sounds as far as the human ear could hear. That made for good music and that's what the amplifier had been built for. So Bronson went home determined to build a series of sharp filters. First he would curtail the band-width of the amplifier until it peaked around eight hundred cycles per second, near the musical note 'A' one octave above the standard Concert Pitch 'A'.