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THE BELL SYSTEM TECHNICAL JOURNAL, APRIL 1951 



end and connected to a bending motor straddles the biasing spring. The 

 permanent magnet can therefore be demagnetized in controlled steps by- 



Fig. 19 — Schematic of automatic ringer adjusting equipment. 



discharging a condenser through the electromagnet and the biasing spring 

 can be bent in controlled steps by rotating the fork. Alternating with these 

 demagnetizing and bending adjustments automatic tests determine what 

 additional adjustments are required. These tests consist of observing photo- 



