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Патент USA US2113148

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April 5, 1938.
Filed Aug. 15, 1935
Patented Apr. 5, 1938
Rudolf Weber, Berlin, Germany, assignor to Tele
funken Gesellschaft fiir Drahtlose Telegraphic
m. b. H., Berlin, Germany, a corporation of Ger
in any
Application August 15, 1935, Serial No. 36,285
In Germany August 29, 1934
3 Claims.
This invention relates to a signal ampli?er in
which, at the appearance of a frequency corre
sponding to a predetermined signal, an indicating
lamp will be illuminated.
It is an object of _my invention to improve upon
signal vresponsive devices of heretofore known
types by providing a system in which the gain in
an ampli?er is variably~ controlled by the received
signals so that if the signal is of one frequency,
10 this gain would be increased, whereas if it is of
another frequency, the gain would be decreased.
Another object of my invention is to provide a
signal ampli?er feeding into an output circuit
which contains preferably a system of glow dis
15 charge tubes, and to provide the means for ex
citing these tubes selectively according to the
potential drop which is produced across their
Another object of my invention is to provide a
system of the character mentioned in the fore
going, in which suitable ?ltering means are also
provided in combination with recti?ers such that
a grid biasing circuit in the ampli?er may be con
trolled positively or negatively according to the
[5 Cl frequency of the received signal which is passed
through one or the other of the ?lters respectively.
By achieving the objectsv of my invention the
heretofore known arrangements will be seen to
have been improved upon in such manner that
certain disadvantages of the prior art will be
overcome. Among these disadvantages may be
mentioned the following:
1. In practice, a single ?lter means is not su?i
cient to obtain a de?nitefrequency, and in order
to provide a satisfactory selectivity, several, at
least two, ?lter means should be placed in series.
This however entails‘ the necessity of a consider
able amount of material.
At the arrival of very strong signals. at the
40 input, it can also happen that other glow tubes
will be simultaneously illuminated thus causing
erroneous signaling, unless a special amplitude
control is provided.
2. Glow tubes as used in systems of the prior art
' in order to be sensitive to signals have usually
(Cl. 177-353)
Fig. 1 shows one embodiment of my invention;
Fig. 2 shows a modi?cation thereof.
Referring ?rst to Fig. 1, I show a preferred
embodiment of my system in which signals may
be impressed upon the primary of a transformer
l and transferred-thence to the input circuit of
an ampli?er tube 2. This tub'e may be a triode,
if desired, but preferably a screen‘ grid tube may
be used as shown. In the output circuit of the 10
tube 2 I may insert two gaseous discharge tubes
4 and, 5 in series with a choke coil 3. The cathode
of the tube 4 and the anode of the tube 5 are
interconnected, andlikewise the cathode of the
tube 5 and the anode of the tube 4 are inter 15
connected. Between the cathode of the tube 2
and one of the common connections between the
tubes 4 and 5, I insert a portion l5 of the direct
current anode potential source which is to be .fed
to the anode of the tube 2 through a resistor 6
and thence through the choke coil 3. Another
portion [6 of this direct current anode source
lies between the ?rst mentioned portion thereof
and the resistor 6. The input circuit of the tube
2 includes a grid bias resistor l3 and a. capacitor
l2 shunting the same.
The values of the anode potential sources I 5 -
and Hi, the ohmic resistance values of the resistor
6 ‘and the choke coil 3, and the value of the grid
bias resistor l3 are all so chosen that the drop
of potential across the resistor 6, when the tube 2
is acting normally and without the impress there
on of any signal, is ‘about equal to the potential
drop internally of the tube 2, that is to say, be
tween the anode and ‘the cathode thereof. In
making this statement, the ohmic resistance value
of the choke coil 3 may be neglected. Also the
?xing of values for the anode potential sources l5
and I6 and for the resistor 6 must be determined
with due consideration for the ignition and ex
tinction voltage ratings of the tubes 4 and 5. In
other words, thevsystem must be made stable when
no signal is coming in so that neither one of the
tubes 4 or 5 will be ignited by a. normal potential
drop ‘across the resistor 6 due to normal current 45
been biased close to the ignition potential and
sometimes above the extinction potential and for
this reason they were subject to ignition improp
erly, incident to disturbing impulses. If auto
matic extinction devices were provided, these
would tend to complicate the device and add to
then it will be possible to igniteone of the tubes
its weight as well as its cost.
The invention will now be described in detail,
This gain control device is coupled to the out
put circuit of the- tube 2 by means of a capacita
reference being made to the accompanying draw
55 ing in which
?ow in the tube 2.v If, however, the impedance
of the tube 2_is either increased or decreased
4 or 5 selectively. The means for accomplishing
this result include a gain control device in cir
cuit with the grid lead to the tube 2. '
tor ‘I so that output energy, or at least some of
‘ it, may be fed through the primaries of two trans 55
formers which are respectively included in two
‘resonant circuits 8 and 9, one of them being
tuned to a predetermined frequency to be used
for signals having one signi?cance and the other
being tuned to a different frequency so that it
producing a more negative bias on said grid in
response to a signal of a frequency to which one
of ‘said circuits is resonant, and a more positive
bias in response to a signal of a frequency to
which the other of said. circuits is resonant,
will respond to signals having another frequency
signi?cance. Energy of the ?rst mentioned sig
nalling frequency may therefore be fed through
is caused to be varied above and below a level of
no-signal-response, and one or the other of said
the resonant ?lter system 8 and through a rec
glow discharge ‘tubes is correspondingly ignited.
10 ti?er l0 which tends to lower the grid bias po
tential on the tube 2 and thus to reduce the cur
rent ?ow therein. Since the tube impedance
rises in response to signals of this frequency, it
whereby the conductivity of said amplifying tube
2. In a diiferentiallyresponsive signal indica 10
tor, a pair of gaseous discharge tubes each hav
ing an anode and a cathode, the anode of each
will be seen that the potential on the anode of
tube being connected to the cathode of the other,
an ampli?er tube network having an input cir
the tube 5 will be increased, and such increase
cuit and an output circuit, said gaseous tubes be- .
being above the ignition voltage of the tube 5,
ing parallel-connected in said output circuit,
this tube will nowbecome ignited in response
‘to the signal.
means including resonant ?lter systems coupled
to said output circuit and unidirectional devices
A signal of the second mentioned frequency
may likewise be received and passed through the
?lter system 9, in which case the output energy
each connected in an opposite sense to that of the
other and between said ?lter systems and said in 20
therefrom may be fed through the recti?er ll so
as to render the grid of the tube 2 more positive.
This will lower the potential of the anode of the
tube 2 and correspondingly render the cathode of
the glow tube 4 more negative, as a result of
which the tube 4 will now become ignited and
tively in response to a signal of one frequency
and negatively in response to a signal of a dif
ferent frequency, and means for causing the re
the tube 5, if it had previously been ignited, will
?er tube impedance is lowered and for produc
now be extinguished. The increased current ?ow
in the tube 2 is at least partly absorbed by a cur
ing an ignition voltage across the other of said
gaseous tubes when the ampli?er tube impedance
rent ?ow through the tube 4, excitation being
provided ‘by means of the battery l5.
is raised.
3. A receiving system having an electron dis
charge tube ampli?er in combination with a pair
Referring now to Fig. 2, I show a modi?cation
~ in‘ which the glow tubes 4 and 5 are placed in
35 series with the transformer primaries of the filter
systems 8 and 9. The resistor 6 occupies the
same position relatively to the connections of the
tubes 4 and 5‘as is shown in Fig. 1. In fact, the
operation of the circuit is similar in most respects
to that of Fig. l and accordingly further descrip
tion of this modi?cation is not necessary.
I claim:
l. A signal responsive device comprising an
amplifying electron discharge tube having a
cathode, an anode and at least one grid; a di
rect current source and an ohmic resistance in
circuit between the cathode and anode; a pair
of asymmetrical glow discharge tubes each con
nected in shunt with said resistance and with a
r '~:tion of said direct current source; means in
cluding resonant circuits coupled to the anode of
said amplifying tube for providing a grid biasing
control potential thereto and means including a
recti?er interposed between each of said resonant
circuits and the grid of said amplifying tube for
put circuit for varying the control grid bias posi
sulting variation in the tube impedance of said‘ 25
ampli?er network to produce an ignition voltage
across one of said gaseous tubes when the ampli
of glow tubes and a pair of resonant circuits cou
pled to the output circuit of said ampli?er, a de 35
vice for exciting said glow tubes selectively in
response to the impress of signals of different
frequency characteristics upon said electron dis
charge tube ampli?er, said device including
means for rectifying a portion of the output en 40
ergy from said ampli?er and for producing there- »
from at times a positive increment in the grid
bias potential applied to said ampli?er when the
received signal is of one frequency, and at times
a negative increment in said grid bias potential
when said signal is of a different frequency, and
means for causing the resultant increase or de-_'
crease in conductivity of the electron discharge
path in said amplifier to control the potential
drop across the electrodes of said glow tubes in 50
such manner that one of them is ignited in re
sponse to a signal of the ?rst said frequency and I
the other of said glow tubes is ignited in response
to a signal of the second said frequency.
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