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<p>The experiments were made with a buzzer as transmitter, capable of giving wave-lengths from 350 m to over 2000 m. The chalcopyrite-zincite (perikon) detector was used as a standard for comparison, measurements showing that the deflections obtained with this detector are proportional to the squares of the oscillatory currents as measured by thermo-element. For the comparison of detectors of other types with the perikon, the shunted telephone method and the variable coupling method were used. With the first method a series of measurements may be made to agree among themselves to within about 10 per cent For the measurements, the buzzer circuit acts upon a second circuit whoso constants are made to%
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<br>Subjects: radiotelegraphy; measurements and use of instruments; Telephony B6210F Telegraphy</div>
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