.-/ Cl.DCK-COXIHOl.l.l-n ICNIXC lOKK 147 



tinu' ititiTN.il i"(|ii,il to till" iuiiiiIht of cycles of the fork wliich \vc 

 (loin- to m.iko ciiiial to the tinu- iiitiT\al lii-twucn successive clock 

 impiilsi's. This is readily accomplished In' means of a phonic wheel 

 or synchronous motor operated l)\' the fork. This motor may he 

 coiinecte<l to any form of g;ear train in order to i;et the necessiiry 

 inteRration. 



The re<iuirenients so far oiilli;KHl do not limit llu- fre(|iieiicy of the 

 fork in an>- degree except that we must be able to integrate its periods, 

 and if a nurhanical means is used as outlined, this probably sets an 

 up{H>r limit on the frequency at 400 or 500 cycles. However, prac- 

 tical considerations will generally make the most siitisfactory fre- 

 cjuency considerably lower than this, since it is an easier matter to 

 compare unknown frecjuencies with a low frequency standard rather 

 than with one of hii;Ii frequency. 



Method of the Control of the F\)Rk hv the Ci-ock 



The fork used in the system described below is of the same type as 

 that tested by Dadourian. It is operate<l by a driving magnet and 

 make and break contact, and was originally designeil for use in mul- 

 tiplex printer telegraph circuits. It can be adjusted to operate at 

 50 cycles and is designed to drive a synchronous distributor which 

 rotates once for every 10 cycles of the fork. By means of a 5 to 2 

 retluction gear and a contact operated by it, an impulse may be 

 obtained once every 25 cycles of the fork. If the fork oscillates at 

 exactly 50 cycles per second, the time interval between the impulses 

 will be exactly one-half second, and this time interval will be shorter 

 or longer, according as the speed of the fork increases or decreases. 



The control system used is designed to affect the frequency of the 

 fork in proportion to the difference between half second intervals as 

 measured by the clock and the time required by the fork to complete 

 25 cycles. Fig. 1 shows the details of this control. F"ig. 2 is the 

 schematic diagram. Referring to Fig. 2 the contact marked "Fork" 

 is the contact obtained every 25 cycles froin the fork and the con- 

 tact markefl "Clock" is that obtained every half second from the 

 clock. Each of these contacts is adjusted to remain close<l for a 

 period of approximately .05 second when operated. 



The control operates as follows. When the clock contact closes, 

 the relay operates and locks until the fork contact closes and short- 

 circuits the winding of the relay which then releases. During the 

 time that the relay is operated, the condenser C is charged through 

 the resistance ri by the battery Bi. The voltage of this battery is 

 such that when applied to the grid of the vacuum tube, it will^just 



