AN IMPROVED TELEPHONE SET 



257 



will also apply over the service life of the dial, hence no field adjustment will 

 be necessary. 



An exploded view of the new dial is shown in Fig. 12. A zinc base die cast 

 frame serves as a mounting for the various dial details as well as providing 

 facilities for mounting the dial in the set. The gear train is a precision as- 

 sembly depending upon careful dimensional control of gears, shafts and 

 bearing plates to insure smooth and dependable operation. The governor 

 assembly is driven through a band type of clutch which decouples the 

 inertia of the governor during "wind-up" of the dial. The drive bar and the 

 weights are sintered brass which results in substantial manufacturing advan- 



MAtN GEAR 

 BAND d-UTCH-i 



:ar train 



^SEMBLY— 5 



( 



SPRlNi 

 BLOCK 



^NUMBER PLATE 



Fig. 12 — View of new dial. 



tages. The pulsing mechanism of the dial consists of a single lobe cam, a pawl 

 and two pulsing springs. The cam and pawl are injection molded of nylon. 

 The pulsing springs as well as the receiver off-normal springs are molded in a 

 phenol plastic block. The springs are held in accurate alignment during the 

 molding process, and adjustn*ent of contact forces is made after assembly 

 of the spring block to the dial. 



Figure 13 shows the general layout of the pulsing mechanism. The cam 

 is fastened to the pulsing shaft which has a 12:1 gear ratio with the finger- 

 wheel. The spacing of the holes in the fingerwheel is such that, if D is the 

 number of the digit dialed, the pulsing shaft and therefore the cam rotate 

 D -f 1 revolutions. The nylon pawl is coupled to the cam shaft through a 

 spring friction drive and rotates with the shaft through the angle /3 between 

 two stops as shown. When the dial is wound up, the pawl moves to Position 1. 



