.■IX lu.r.cTRiCAi. i-Rr.oin-xcY axai.y/.er 31.1 



to its st.irtiiis; condition. Tliis is .iix'oini)lislK<i 1)\- iihmiis of a per- 

 foration at till- t-nd of tlu' record which admits air to chamber M of 

 the main control rel.u', thus closing contacts /. Kehiy .S then operate^ 

 since its circuit to ground is completeti tiirough contacts P. Oper- 

 ation of rchiy 5 opens contacts T thus disconnecting lamps // and 

 /, and closes contacts U and 1'. It will be seen that the closing of 

 contacts. {' operates the reversing mechanism, and rewinding of the 

 roll begins immediately. The closing of contacts V operates the 

 slide valve thus releasing the vacuum on the main header, allowing 

 the roll to be rewound with minimum mechanical drag. 



It may be noted that means are also provided for rewinding the 

 roll from any point in its forward travel by admitting air manually 

 at the reversing key. This will cause the main control relay to 

 operate so that rewinding will begin. Vacuum is kept on the aux- 

 iliar\- header during the rewind so that control of the analyzer may 

 be maintained to the end of the operating cycle. 



When the paper has been completely rewound perforations allow 

 air to enter simultaneously chamber of the main control relay and 

 chamber A' of the holding relay. This action opens contacts J and 

 A', thus bringing the entire mechanism to rest in its initial starting 

 condition. 



Applic.\tions 



To show the variety of problems in which the analyzer is a useful 

 means of investigation, a few illustrative records have been made 

 and will be discussed. These records were taken in each case to 

 illustrate the use of the analyzer and are not parts of investigations 

 to which they are related. They cannot, therefore, be taken as 

 representative of the performance of the apparatus tested. 



One of the uses of the analyzer has been in the study of the per- 

 formance of microphone buttons. Fig. 8, for example, illustrates 

 the character of the distortion in a button when driven at an excessive 

 amplitude. The button was mounted so that its movable electrode 

 could be dri\en at a single frequency by a very heavy reed at its 

 natural frecjuency so that the motion was very nearly sinusoidal. 

 The frequency of the motion was a little less than 450 cycles cor- 

 responding to the second peak on the record. The amplitude of 

 motion was 0.001 centimeters or 0.0004 inches which is of course 

 much greater than normally obtains in a transmitter. The circuit 

 consisted simply of the button and a battery in series with the ana- 

 lyzer so that the record is an analysis of the current fluctuations in 

 the button. The record shows two series of frequencies generated 



