A GOVERNOR FOR TELEPHONE DIALS 



1301 



Table V — Type Dla.l Governor Input Torque at Pulse No. 5 



Average 7,500 dyne-cm, approximately. 



position, thus eliminating the gravity effect. The deflection of the 

 governor spring measured on the photograph was used to determine the 

 Fg force, and the governor speed, necessary to determine Fm , was taken 

 from the oscillograph string trace. Three dials were tested, each having 

 the same maximum motor spring torque, 490,000 dyne-cm, and clean 

 governor cases and studs to produce an assumed coefficient of friction 

 value, u = 0.25. For three 7-type dials with fly-bar governors, the ex- 

 perimental data given in Table V applies. 



As determined, this 7,500 dyne-cm torque at the governor exists at 

 the middle of rundown of the dial. In order to compare it with the 

 13,500 dyne-cm initial torque previously determined, it is first necessary 

 to consider the effect of the motor spring. As stated previously, the torque 

 provided by the motor spring during dial rundown decreases approxi- 

 mately 35 per cent from the initial value of 490,000 dyne-cm. Logically, 

 the torque at the governor would decrease by the same percentage. 

 Applying this factor to the torque value for the middle of rundown gives a 

 value of 10,500 dyne-cm which can be compared with the 13,500 dyne-cm 

 torque. A difference of 3,000 dyne-cm exists for the value of initial torque 

 at the governor as determined by the two test methods. This remaining 

 difference can be explained by considering the frictional losses in the dial 

 mechanism during rundown. This analysis follows: 



During rundown of the dial mechanism, a pair of pulsing springs ten- 

 sioned against components on the pulsing shaft are alternately raised 

 and lowered. This action allows contacts on the springs to open and close 

 for pulsing in the telephone line. A portion of the input torc^ue provided 

 by the motor spring is required for performing this function. On Fig. 14 

 are plotted the torque curves for these pulsing springs as the pulsing 



