RADIO EXTENSION LINKS TO TELEPHONE SYSTEM 



627 



the delay circuits of the Vodas are unnecessary. This arrangement is 

 finding increased application in ship-shore terminals. 



Referring again to Fig. 5, note two squares in the first diagram 

 labeled "Compandor." ^ Each of these squares has part of the name 

 dotted to indicate that the two circuits are different but together form 

 the entire Compandor. The Compandor is another device to assist in 

 making signals more intelligible in the presence of noise at the receiver. 

 It accomplishes this by the peculiar method of distorting the signal 

 going out and then restoring it at the receiver. The reason for such a 

 device and its mode of operation are as follows. Ordinary speech 

 contains loud as well as weak signals. Most of the consonants and 

 some of the vowels do not contain much energy. They therefore 



A/Vv 



AAAr 



■AAA. 



Fig. 10 — Compressor part of the compandor. 



will not modulate the transmitter fully and are the ones whose re- 

 ception will be interfered with by noise at the receiver. The Com- 

 pandor reduces this effect by making the weak parts of the transmitted 

 signal larger than normal. 



The part of the Compandor in the transmitter branch distorts the 

 speech signal by reducing the energy variations between the loud and 

 weak sounds a certain amount. It does not wipe out all variation as 

 it is necessary to leave a certain variation which is made use of at the 

 receiver to restore the original variation. The circuit used at the 

 transmitter end is given in Fig. 10. It is called the Compressor. 

 A speech signal comes in on the left-hand side and goes out on the 

 right. Between the input and output circuits are connected two 

 vacuum tubes. Although superficially this circuit looks as though 

 these tubes are amplifiers, actually they are connected to absorb 



