FREE BOOKS

Author's List




PREV.   NEXT  
|<   43   44   45   46   47   48   49   50   51   52   53   54   55   56   57   58   59   60   >>  
tance in a telegraphic circuit, a sound of a given pitch. It is therefore a true telephone. REISS' TELEPHONE. The ease with which membranes are thrown into vibrations corresponding in period to that of the sounding body has already been alluded to on p. 80; and several attempts have been made, at different times, to make membranes available in telephony. The first of these attempts was made by Philip Reiss of Friedrichsdorf, Germany, in 1861. His apparatus consisted of a hollow box, with two apertures: one in front, in which was inserted a short tube for producing the sound in, and indicated by the arrow in the cut, Fig. 12; the other on the top. This was covered with the membrane _m_,--a piece of bladder stretched tight over it. Upon the middle of the membrane, a thin piece of platinum was glued; and this piece of platinum was connected by a wire to a screw-cup from which another wire went to a battery. [Illustration: FIG. 12.] A platinum finger, S, rested upon the strip of platinum, but was made fast at one end to the screw-cup that connected with the other wire from the battery. Now, when a sound is made in the box, the membrane is made to vibrate powerfully: this makes the platinum strip to strike as often upon the platinum finger, and as often to bound away from it, thus making and breaking the current the same number of times per second. If, then, a person sings into this box while it is in circuit with the afore-mentioned click-rod and box, the latter will evidently change its pitch as often as it is changed by the voice. In this apparatus we have a telephone with which a melody may be reproduced at a distance with distinctness. But the sounds are not loud, and they have a tin-trumpet quality. If one reflects upon the possibilities of such a mechanism, and upon the conditions necessary to produce a sound of any given quality, as that of the voice or of a musical instrument as described in preceding pages, he will understand that it can reproduce only pitch. It might here be inferred that something more than a single pitch is transmitted if the sound is like that of a tin trumpet as stated: but the reason of this is that, whenever a current is passing between two surfaces that can move only slightly on each other, there is always an irregularity in the conduction, so as to produce a kind of scratching sound; and it is this, combined with the other, the true pitch, that gives the character to the sound
PREV.   NEXT  
|<   43   44   45   46   47   48   49   50   51   52   53   54   55   56   57   58   59   60   >>  



Top keywords:

platinum

 

membrane

 

apparatus

 

current

 

produce

 

trumpet

 

quality

 

battery

 
connected
 
finger

attempts

 
telephone
 

circuit

 

membranes

 

irregularity

 
reproduced
 

scratching

 
distinctness
 

sounds

 

conduction


distance

 
mentioned
 

character

 
person
 

combined

 

changed

 
evidently
 

change

 

melody

 

reason


reproduce
 

understand

 
preceding
 

stated

 

transmitted

 

inferred

 

instrument

 

musical

 

reflects

 

possibilities


slightly

 

single

 
surfaces
 
passing
 

mechanism

 

conditions

 

Friedrichsdorf

 

Germany

 

Philip

 

telephony