First progress report on a multi-channel magnetic drum inner ...

a) Be capable of operation from, and into, easily
III-6
realizeable external electrical circuits at a repetion rate of one
megacycle.
This implies low terminal impedance; specifically, low enough to afford
A-1) Recording current rise and fall time on the order
of a fraction of a microsecond upon application and
removal of perhaps 100 volts.
A-2) Reading out as a voltage generator, to drive a
low impedance transmission system—say a cable and
amplifier imput capacitance on the order of 10 to
100 M.M.Fo without appreciable attenuation.
B) Interaction bet.icen heads when recording and sensitivity
to external field disturbances when reading should be as low as possible.
This implies low stray field and leakage flux, accompanied by relatively
close coupling with the magnetic medium to be inscribed; specifically:
B-1) Recording at normal current strength via any head shall
not produce any appreciable interaction or effect
upon the track of neighbors located as close as per-
haps 1/ k inch center to center.
B-2) No appreciable increase in noise level due to pickup
from normal stray fields of the laboratory.
C) Heads should be simple to construct and maintain, inexpensive
and compact enough to permit ready arrangement in gangs, etc.
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