Lever b turns about fixed axis B. When lever b is to be shifted, its member 1 is pressed with the hand, turning this member about pin A. This withdraws latch 2 which is connected by pin a to member 1 and slides with a certain clearance in guide 3. In the required shifted position of lever b member 1 is released and spring 5 returns latch 2 into the corresponding slot of segment 4.
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