. Scientific news for general readers; a popular illustrated weekly journal of science . rse,for voices of varying loudness and pitch. Generallyspeaking, a lighter pressure is best for high-pitched voices,such as those of women and children ; a heavier pressureis necessary if the instrument is to be used by men, whosestrong deep tones tend to set the springs into too greatvibration, causing complete interruptions of the current,and producing an unintelligible growl or a succession ofsharp cracks in the distant receiver. There are otherforms of variable resistance transmitters inuse, notably Ad
. Scientific news for general readers; a popular illustrated weekly journal of science . rse,for voices of varying loudness and pitch. Generallyspeaking, a lighter pressure is best for high-pitched voices,such as those of women and children ; a heavier pressureis necessary if the instrument is to be used by men, whosestrong deep tones tend to set the springs into too greatvibration, causing complete interruptions of the current,and producing an unintelligible growl or a succession ofsharp cracks in the distant receiver. There are otherforms of variable resistance transmitters inuse, notably Aders, a microphone-form much in use on theContinent, and Professor Silvanus Thompsons valve tele-phone, which is a very peculiar form, consisting of a tinymetallic or carbon ball standing on three little legs, at theupper end of a tube leading from the mouthpiece, andturning up by a gentle curve. The action is produced bythe air waves—somewhat concentrated, no doubt, by theshape of the mouthpiece—passing up the tube and beatingon the lower surface of the ball, varying the pressure. between it and its supports, and so varying the electricalresistance between them. This transmitter speaks verywell, and it is unique among modern instruments in follow-ing Reiss example, and sometimes using metallic Thompson has, however, found some difficultyin getting a metal free from the practical drawbacksmentioned in describing Reiss instrument, and now usescarbon contacts. He claims to have made a good workingtransmitter, and it has already met with a certain amountof commercial success. One form is illustrated in Fig. 1 j,where A is the tube provided with a flaring mouthpiece,V the valve, egg-shaped in this instrument, and P thesupports. The valve and supports are shown in plan tothe right of the general section. This is practically amicrophone with three contacts, but the current passesfrom centre to circumference, or vice-versa; the coiled wireconnection to the valve
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Keywords: ., bookcentury1800, bookdecade188, bookpublisherlondon, bookyear1887
