I 



•ruF. snmioi'iioxi:." ./.v electrical stei iioscoi'e 5J7 



M'nil>lini; a "ttM-way;nn." I( rc(iiiiri-s fur its opiT.ition ,i >.i\-\()lt 

 storage iKitti-ry and a i;it)-v()ll "B " battery. These are housed in 

 roiiipartinents in the hiwer part of the cabinet. Ten jack positions 

 are pro\ ided to (uTiiiit tliis iiiinilter of persons to hsten simiiltaiK-oiisly 



E^=Ufj 



Kii;. 4 — ("irciiit diagram of stcthophonc 



around the stcthophone. All controls arc coinciiieiiiK jjlaecd on a 

 single panel to facilitate operation. 



.A schematic circuit diagram is shown in l-"ig. 4. 



4. Tr.\nsmitter 



The transmitter employed with greatest success with the stctho- 

 phonc thus far is of the electro-magnetic type equipped with a special 

 \ibrator>- element which is placed in direct contact with the flesh 

 of the patient. 



One of the features of the transmitter is its insensitiveness to sound 

 waves in the air. Thus, the ratio of extraneous noise picked up 

 by the transmitter to the body sounds is greatly reduced so that 

 observations can be made with a minimum amount of interference 

 from rot)m noise. 



The transmitter construction provides efficient transfer of vibra- 

 tional energy from the flesh or bony framework of the body to the 

 vibrator^' steel element. It provides a means for coupling which 

 serves as a mechanical transformer for body sound energ>' and avoids 

 an abrupt change in the path of the waves and large attendant losses 

 by reflection. The system is highly damped and minimizes the dis- 

 tortion of the sounds of interest. 



Since the transmitter is a contact device, the physician may vary 

 the pressure of application at will. Firm but light contact is desirable. 

 The human flesh contributes damping to the vibratory system of the 



