5.
Construction and operation of erase head. The erase head removes any prior
recording and leaves the tape quiet so that it may be used again.
a. The erase head functions exactly the same as the record head.
It is
constructed with a relatively large gap, which allows the flux to leak out over a
relatively large longitudinal area in the tape path.
b. We send a high-frequency AC to the head.
As a point on the tape
approaches the gap, the alternating magnetic field gets stronger and stronger until
a maximum magnitude is reached directly at the gap.
c. The high frequency sent to the head is far above the audio range.
The
erasing field will disappear before out point on the tape approaches the record
head.
6.
Construction and operation of reproduce head. Although the reproduce head is
constructed almost the same as the record head, it functions more like an electric
a. When we move a conductor through a magnetic field, as we do in a
generator, we induce in that conductor a voltage whose amplitude and polarity are
functions of the magnitude and direction of the magnetic field.
b. We can, of course, achieve the same results by passing the magnetic field
across a stationary conductor, as the only requisite is that the conductor must cut
the lines of force.
7.
When we move the recorded tape past the gap in a reproduce head (fig 1-13)
the magnetic flux on the moving tape will induce a voltage in the head coil.
a. This induced voltage will be proportional to the number of turns on the
head coil, the permeability of the core material and the time rate of change of the
magnetic flux.
b. In reproducing information from a recorded tape, one important factor is
the dimension of the reproduce head gap. The gap in the reproduce head is .00025
inch.
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