260 



THE BELL SYSTEM TECHNICAL JOURNAL, APRIL 1951 



Ringer 



The ringer of the new telephone set, Fig. 16, uses a single coil with a lam- 

 inated silicon steel core instead of the two coils used in previous type ringers,® 

 thus obtaining an appreciable saving in copper. The single coil has two wind- 

 ings which make it possible to use the same ringer and set for a variety of 

 service conditions including individual or two-party message rate service. 



22 



20 



18- 



10 20 30 40 50 60 70 80 90 100 X 10^ 



GOVERNOR INPUT TORQUE IN DYNE -CM 





COEFFICIENT OF FRICTION,// 



Fig. 15 — Dial speed vs. torque and coefficient of friction. 



Instead of the usual U shaped magnet, the new ringer employs a small 

 cylindrical magnet of Alnico V, which results in considerably higher perma- 

 nent magnet flux. 



In addition to providing the required operating characteristics, such as 

 adequate sensitivity and protection against cross ring and bell tapping, it is 

 desirable to be able to use more bridged ringers on a single line than is possi- 

 ble at present in some types of central offices without pretripping of ringing. 

 This means that the new ringer must have much higher impedance at ringing 



