Advertisement
result can be obtained by threading a
wire through the center of the core.
If
a sufficiently strong current is passed
through the wire, the core will be mag-
netized by virtue of the magnetic field
created around the wire as the current
passes through the wire.
If the current
through the wire is reversed, the core
becomes magnetized in the opposite
direction (Figure 2-40).
Thus, by con-
trolling the direction of current flow
through the wire, it is possible to
magnetize the core to a value of either
binary 1 or binary O.
Changing the core
from one magnetic polarity to another is
called flipping the core.
+
Figure 2-40.
Magnetic Core
Using one wire fo.r each core results
in an expensive, inefficient storage
device.
With a slight change in the
method of flipping the cores, it is
possible to produce a more efficient
device.
1/2 Current
1/2 Current
+
+
Figure 2-41.
Half-Current Principle
TWo-Wire Addressing
•
Two wires pass through each magnetic
core.
•
Core is magnetized by additive
effects of the two magnetic fields.
By passing two wires through the core,
and by sending just half the current
necessary to magnetize the core through
each wire, the core is flipped by virtue
of the additive effects of the two mag-
netic fields (Figure 2-41).
If this half-current is passed
through just one wire instead of both
wires, the core is not flipped because
the magnetic field is not great enough.
Thus the core can be affected only by
the coincidence of the two
half-currents.
This half-current principle can be
used to simplify the setting of cores by
forming a screen of wires with a magnet-
ic core at each intersection of the
wires (Figure 2-42).
By sending current
in the appropriate direction through the
appropriate pair of wires, the desired
core can be flipped to the desired mag-
netic polarity without affecting the
other cores in the group.
2-29
Advertisement
