Word: taping
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Dates: during 1970-1979
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Picking up a pointer, Bolt explained a large chart that presented the panel's findings in graphic form. A principal technique used in arriving at their conclusions, he noted, was to develop the tape "in a sense that you develop a picture." A fluid containing magnetically sensitized particles was rubbed over the tape. The particles arranged themselves in conformity to magnetic imprints previously induced on the tape by electronic signals in the original recording and erasing processes. Thus the imprints could be seen with the naked eye and photographed. Bolt also noted that the signals had been analyzed by oscilloscope...
...Signature. Speaking animatedly and in a high-pitched voice, Bolt explained the rudiments of a tape recorder's operation. When the "record" and "start" buttons are pushed, the tape rolls past two "heads" containing tiny electromagnets. The first, the erase head, eliminates most previous signals on the tape. The second, the record head, implants new signals. On the Uher, the two heads are "rigidly fixed" at 28.6 mm. apart. When the erase head is released on the Uher (but not on all recorders) it leaves a minute but discernible four-line "signature" on the tape. This mark is distinctive...
...cheerily demonstrated that once the record button is depressed, it "locks itself down." It can be released only by pushing any of four other buttons: "start," "fast forward," "rewind" or "stop." If a foot pedal is used to control the recorder, the lifting of a foot will cause the tape to stop moving, but will not result in the erase head's leaving the telltale four-line "off' signature...
When they developed the 18-minute segment of tape, the experts found five of the "off' signatures, indicating that while the record button was down, it had been manually released at least five times by pushing other buttons. Each of these "off' signatures was preceded on the tape, logically enough, by an "on" mark. That meant that someone had pushed three buttons (two to start, one to stop the erase-record process) at least five times (see chart...
Another major conclusion of the panel was that the 18-minute section of tape "probably contained speech originally." The evidence for this is that the scientists found three tiny "windows" on the tape?minute sections in which the buzz did not appear. Although undetectable by an untrained ear, they found in each of the windows "a fragment of speechlike sound lasting less than one second." These sections apparently were missed by the erase head in the multiple manipulations of whoever tampered with the tape. Bolt explained that the assumption that speech underlies the entire buzz is basically "a statistical argument...