LOAD RATING THEORY 



631 



mitters. It is also the custom to provide a certain amount of ampli- 

 tude limiting in each channel by suitable circuit design of the channel 

 terminal equipment. This limiting alters the shape of the instantane- 

 ous voltage distribution curve for a range of voltages below the maxi- 

 mum, the extent of the modification depending on the talker volume 

 and the characteristics of the limiting device. Its effect on the load 

 capacity will be considered later. 



0.9 

 0.8 



■ in 0.5 



CO 



< 



0.10 



0.09 



0.08 



0.07 



0.06 



0.05 



0.04 



0.03 



0.02 



0.01 



0.5 1.0 1.5 2.0 2.0 2.5 3.0 3.5 4.0 



RATIO OF RECTIFIED INSTANTANEOUS VOLTAGE TO RMS VOLTAGE 



Fig. 2 — Instantaneous voltage distributions for n talkers. 



Multi-Channel Instantaneous Voltage Distributions 

 The number of variables with which it is necessary to deal makes 

 the general load capacity problem rather a complicated one. The 

 analysis .will be easier to follow if the effects of the different variables 

 are taken up one at a time, thus building up a complete theory in 

 successive steps. To do this, it is advantageous to start with a case 

 so simplified that it rarely, if ever, occurs in ordinary practice; i.e., 

 that in which the volumes in all the channels are regulated to a common 

 constant value, and in which the number of active channels is also kept 

 constant. For this condition, it is necessary to consider only the 

 effects of the distribution of instantaneous voltages in each channel. 

 This distribution curve is the same for all of the channels, since all 

 are at the same volume, but the voltage in any channel at a particular 

 instant is entirely independent of the condition of the other channels. 



Overload Expectation 

 The total voltage Impressed on the amplifier by a number of channels 

 at a given instant is the sum of the instantaneous voltages in the 



