DOC. 203
APRIL
1910
151
to
insert
an
acoustic
resonator
of
variable
pitch
between
the
telephone
and the
ear.
This
would
be,
in
my view,
a
reliable
way.
The
momentary frequency
of the buzzer
would
follow from
the
setting
of the
resonator.
If
this
is
of interest
to
you,
we can
try
to
press
forward
along
this
route.
Perhaps
I will entrust
a
doctoral
candidate
with
the
study
of
this matter.
Your results
with the transformers
are
not
surprising.
The
simple
formula
for the
reduced resistances
holds
only
under
a
certain
N1 N2
condition.
If
we
denote
by
w resistance
in
the
primary
(I
set
the resistance
in
the
secondary equal
to
zero
because
it
is
easy
to
take
account
of
N1
N2
number of
turns
f
resulting
field
fl
magnetic
resistance of
the transformer
(easy
to
calculate in
that
one
divides
the
magnetic
resistance of the iron-free
coil
by
10.
Thus,
approximately,
XI
=
-
length
of
coil
10
.
core cross
section
i1
i2
alternating current
intensities
p applied alternating
voltage
nf
=
i2N2
+
i1N1
$
-N1
-
=
i1N11
x
dt
-N2-
+
p
=
0
2 dt
Leakages
have
been
neglected
here. If
one
sets
0)
=
2vn
&
j
= -1,
one
obtains[1]