| 摘要 |
A magnetic field generating apparatus for generating a biasing magnetic field applied to master and slave tapes superposed each other for transferring information signals recorded on the master tape to the slave tape, the apparatus comprises a rotary cylinder having a high magnetic permeability on its surface, a main magnetic pole disposed to confront the rotary cylinder for projecting the biasing magnetic field toward the rotary cylinder through a gap defined by a first predetermined distance, a sub-magnetic pole magnetically connected to the main magnetic pole, the master and the slave tapes are depressed to the rotary cylinder by compressed air, and an exciting source for exciting the main magnetic pole to generate the biasing magnetic field, wherein the sub-magnetic pole comprises at least one side-core disposed at a side of the main magnetic pole a second predetermined distance apart therefrom, the side-core confronts with and extends along the rotary cylinder, the second predetermined distance is substantially larger than the first predetermined distance, and a confronting area of the side-core facing to the rotary cylinder is substantially larger than a confronting area of the main magnetic pole facing to the rotary cylinder. An angle of the line of uniform flux density zone formed in front of the main magnetic pole with respect to a rotation axis of the rotary cylinder, can electrically be controlled by making the main magnetic pole being bifurcated to have two legs and exciting them differently each other.
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