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Патент USA US3162743

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Dec. 22, 1964
3,162,728
R. E. PFISTER _
STEREO-SOUND REPRODUCING DEVICE
Filed Nov. 2, 1962
"In
INVENTOR.
J1
?le/‘zigzag,
United States Patent Office
1
3,162,728
STEREO-SOUND REPRODUCING DEVICE
Robert E. Plister, 1170 Logan Ave., Elgin, Ill.
3,162,728
Patented Dec. 22, 1964
2
An audio frequency transducer 44 is connected by leads
22 to the secondary of transformer 20 whereas the second
ary of transformer 18 has a pair of leads 23 connected
to a 1.3 volt lamp 24 for a purpose to be explained
Filed Nov. 2, 1962, Ser. No. 234,965
presently. Similarly, leads 25 connect a second audio
1 Claim. (Cl. 179-4)
frequency transducer 26 to the secondary of transformer
The present invention relates in general to improv
21, and leads 27 connect the secondary of transformer
ments in sound reproducing equipment and is more spe
19 to a 1.3 volt lamp 28 for purposes also to be explained
ci?cally concerned with improved stereo-type of sound
presently. The inclusion of these low voltage lamps, one
reproducing apparatus, such as a stereo-record player,
in each channel circuit, results in no noticeable loss of
having remote speaker means selectively connected with 10 gain. A pair of ganged switches 29 arranged in the
one output channel and including novel means for elimi
input circuits to the transformers affords means to effec
nating channel interference and extraneous record surface
tively make the lamps non-functioning in instances of
noise.
use when their function is not desired.
In known stereo-type sound reproduction, the inactive 15
Leads 215 to audio frequency transducer 26 includes a
output transducer or speaker has a tendency to emit
jack switch 31 into which may be inserted a jack 32
sounds of channel interference and spurious record surface
having ?exible leads 33 of any desired length connected to
noises. This is particularly annoying when one considers
an auxiliary audio frequency transducer 34- which pref
that in a system intended for children’s use, the records
erably is enclosed in the body of a doll or other character
will accumulate a certain amount of surface noise over a
20 representation 35. Preferably, and for full effect, the
short period of time. This surface noise, when present
character representation 35 is in substantial conformance
in the inactive audio frequency transducer would have a
with the subject of the stereo recording. The effect of
detracting effect upon the active audio frequency trans
animation by use of the doll representation may be
ducer were it allowed to exist. In order to eliminate such
unwanted sound, applicant has provided novel means to
decrease the input gain to the inactive audio frequency
enhanced by providing the body of said representation
with an opening 36 to permit the insertion of the oper
ator’s hand or ?ngers for manipulating features of the
ampli?er and it is one of the objects of the invention
representation.
to accomplish this result.
In use, insofar as described, only one channel of the
Another feature of this invention is the effective re
stereo-record player is audible at any one time. For
moval of so-called cross channel modulation. The novel 30 example, the channel connected with transducer 21 may
means provided herein effectively removes this type of
be utilized to emit background sounds or to be inaudible,
unwanted sound and is one of the objects of this in
whereas the channel including transducers 26 or 343 may
vention.
emit spoken words, vocal accompaniment or be silent.
The invention also contemplates the provision of a
When only one channel is active it is the purpose of this
modi?ed stereo-record player ampli?er system having 35 invention to eliminate all channel interference such as
therein means to separate the audio output of one of the
extraneous record surface noises and cross channel modu
two stereo channels and deliver it to a remotely placed
lation normally emitted from the audio transducer that
audio transducer connected into one channel. As one
is not active.
example of a use of this arrangement the remotely placed
To accomplish this each lamp 24, 28 has associated
audio transducer may be arranged in the body of a 40 with it so as to be in?uenced by the degree of light
dummy representative of, for example, a doll or animal,
emitted from the related lamp, a cadmium sulphide vari
and of a type and character to match the story or sound
able resistance type photocell 37, 38 respectively. These
produced in the selected channel. The audio output of
photocells have a dark resistance of approximately 10
the other channel is delivered to the usual audio fre
megohms which lowers to about 200 ohms in strong light.
quency transducer of the system and, if desired, the
Preferably, a re?ector 39 is associated with each lamp and
remote ampli?cation can be terminated at will and the
each lamp-photocell assembly is enclosed in a light-tight
audio output formerly fed to the remote transducer can
case 41 for maximum light absorption by the photocell.
be directed to the second- audio transducer in the player.
The output of one photocell, for instance photocell 37,
Another object of the invention is to provide such a
is placed across the input circuit of audio frequency
system.
50 ampli?er 17, through lead 4-2. The output of the other
Another object is to provide a stereo-record player and
photocell 38 is placed, by lead 43, across the input circuit
remote audio transducer combination of the character re
of audio frequency ampli?er 16.
ferred to.
Because each photocell perceives light only from the
The structure by means of which the above noted and
lamp with which it is associated, the resistance varies
other objects and advantages of the invention are attained
inversely with the light strength. Therefore, the stronger
will be described in the following speci?cation, taken in
the light the lower the resistance of the related photocell.
conjunction with the accompanying drawings showing a
Now, because the photocell 37, for example, is connected
schematic representation of a stereo-record player and
across the input to ampli?er 17, there is a decrease in
representative illustration of electronic components and
input gain to this ampli?er when the output of audio
a character representation associated therewith for carry 60 frequency transducer 44 is active and visa versa.
ince
ing out the features of the inventionl
,
the dark resistance of the photocells is high, their con
Referring to the exemplary disclosure of the invention
nection with the input to the respective ampli?ers does not
shown in the accompanying drawings, the stereo-system ‘
affect the signal so long as no modulation is present on
includes any conventional type of stereo-record player in
the opposite ampli?er. When audio is present in a given
cluding a stereo pickup cartridge 11 and conventional 65 transducer and the resistance of the photocell is reduced,
potentiometers i2, 13 arranged in input lines 14, 15
a reduction of gain in the other channel is noted. In
to audio frequency ampli?ers 16, 17 respectively. The
this manner any interference and spurious record surface
output from said ampli?ers is connected to the series
noise in either channel is completely eliminated while the
hook up output audio frequency transformers 18 and 20,
other channel is active, the exact degree of elimination
19 and 21 respectively. In the present instance each 70 being dependent upon the percent of modulation present
transformer 18, 19, 20 and 21 has a secondary impedance
in the opposite channel. Photocell saturation occurs at a
of about 3.5 ohms.
'
level just below normal room volume hence, as long as
3,162,728
4
3
each audio frequency ampli?er speakers, one connected
the volume controls 12, 13 are in a normal listening posi
tion, or above, the system will function satisfactorily. At
any level less than normal, cross channel interference and
to the output of one transformer of each pair of trans
formers, a photo-cell connected to the input circuit to
record surface noise is of no consequence
the audio frequency ampli?er in one ampli?cation system,
a light source for said photo-cell connected to the sec
It might be noted also that due to the slightly delayed
return response of the lamp and photocell at saturation,
ondary of the other audio frequency transformer in the
pair of transformers in the other ampli?cation system
input to the opposite ampli?er is completely attenuated
effective when the speaker in said other ampli?cation
not only during modulation of the opposite ampli?er but
system is active to attenuate signal input to the ?rst named
also during short pauses between words and phrases.
It will be apparent that when either audio frequency 10 audio frequency ampli?er, and switches in the circuits to
said light sources operative to shunt the respective trans
transducer is active, the opposite transducer is inactive and
formers to render the respective light source ineffective.
that substantially all unwanted noise normally emitted
from the inactive transducer is eliminated and that for
normal speech, audible in one channel, the opposite
channel will remain silent.
15
Although applicant has disclosed herein a representa
tive embodiment of the invention, it is to be understood
that the disclosure is by way of illustration and not limita
tion and that the invention is capable of embodying a
variety of modi?cations. in detail structure and application 20
without departing from the spirit and scope of the
appended claim‘
What I claim and desire to secure by Letters Patent
of the United States is:
In a stereo-record player of the type including a dual 25
audio frequency signal ampli?cation system, an audio
frequency ampli?er in each system, a pair of‘ audio fre
quency transformers connected in series to the output‘ of
References Cited by the Examiner
UNITED STATES‘ PATENTS
2,110,358
3/38
Dreisbach ____________ -_ 179-1
2,205,447
6/40
Wallace et a1 __________ __ 179—1
2,247,329
2,335,575
6/41
11/43
Deitz ________________ __ 179—-1
Bierwirth _____________ __ 179-1
2,379,768
7/45
Van Wynen ________ __ 179-—170.6
2,495,809
2,748,201
2,839,616
1/50
5/56,
6/58
Graham ______________ __ 179-1
McMillan ___________ __ 330—84
MacMillan __________ __ 330-59
3,020,488
2/62
De Miranda et al. ____ __ 330~59
3,047,670
3,079,463
7/62
2/63
Gardner ______________ __ 179-1
Feldman ____________ __ 179—1.5
ROBERT H. ROSE, Primary Examiner.
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