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June 8, 1943-
H. v. ALEXANDERSSON ETAL
2,320,996
REMOTE CONTROLSYSTEM
Filed April 14, 1941 '
4 Sheets-Sheet l
. /47
INVENTOR
Cowman? Form? HA/GMS
June 8, 1943.
H. v. ALEXANDERSSON‘ EI'AL
2,320,995
REMOTE CONTROL SYSTEM
Filed April 14, 1941
4 Sheets-Sheet 2
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D/ 75
(‘w/0:11am ?ora?
HA/GLE
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INVENTOR
M .44” Z4; 2 I
BY
W
June 8, 1943.
H. v. ALEXANDERSSON ETAL
2,320,996
REMOTE CONTROL SYSTEM >
Filed April 14, 1941
4 Sheets-Sheet 3
OR
M
I Z
5'’ ATTURNM
June 8, 1943.
H. v. ALEXANDERSSON ETALT
2,320,996
REMOTE CONTROL SYSTEM
Filed April 14, 1941
/
4 Sheets-Sheet 4
/
INVENT R'
I
Ww?'k?
2,320,996
Patented June 8, 1943
UNITED STATES PATENT OFFICE
2,320,996
REMOTE CONTROL SYSTEM
Harald Valdemar Alexandersson, Lidingo, and
Carl-Erik Granqvist, Stockholm, Sweden, as
slgnors to Aga-Baltie Radio Aktiebolag, Stock
holm, Sweden, a corporation of Sweden _
Application April 14, 1941,.Seria-l No. new
In Sweden April 15, 1940
(Cl. 172-239)
lator il, a discriminator II, a direct current
Our invention relates to remote control appa
7 Claims.
amplifier 2|, a motor 2i for causing the move
ratus.
In remote control systems it has been proposed
to arrange a transmitter in such a way that it
transmits a radio-frequency alternating current
the frequency of which is determined by the
position of the transmitter control, and to ar
range a receiver for the transmitted radio-fre
quency alternating current which is provided
with automatic arrangements for tuning ‘to the
transmitted frequency, the automatic tuning ar
rangement being connected to the object to be
controlled according to the momentary position
ment of the secondary parts, to be controlled,
and finally a tuning circuit 22 for the modulator
oscillator, said tuning circuit being actuated by
the motor 2i together with the secondary part 8.
For the sake of simplicity it has been assumed
that a common valve of a well known type is
used both as modulator and oscillator. This
.valve ll contains a cathode 23, an oscillator grid
24, an oscillator anode 25, a, first screen grid 28,
a modulator grid 21, a second screen grid 22 and
an anode 29.
The oscillator tuning circuit 22, consisting of
In remote control systems of this kind it is 15 coil 22 and tuning condenser 33, is connected
between the grid 24 and the cathode 23 of the
suitable to tune the transmitter and the receiver
valve it, through a grid condenser 30 and a grid
by means of tuning circuits, containing fixed in
leak II. The oscillator anode 25 is connected to
duction coils and variable condensers, the shafts
the plus terminal oi’ the main through a reaction
of which are connected to the transmitter con
trol and to the object to be controlled, respec 20 coil 34. By this arrangement oscillations are pro
duced in the internal system of the valve l8, said
tively.
.
oscillations being modulated by the oscillations
Fig. 1 is schematic diagram of the known ar
of the transmitter control.
>
rangement.
Figs. 2 and 3 are diagrams illustrating the
operation of the system of Fig. 1;
Fig. 4 is a schematic diagram of a transmitter
embodying the present invention;
received from the transmitter which are im
pressed on the control grid 21 of the external
system to produce an interference oscillation of
beat frequency similar to the operation of super
heterodyne radio receivers.
In the anode circuit of the valve ll is included
Fig. 5 is a diagram illustrating the operation
a transformer which is tuned to the beat fre
of the transmitter of Fig. 4;
30 quency. This transformer is made as a dis
Fig. 6 is a schematic diagram of a receiver (or
criminator, that is, it is sharply tuned to the beat
use with the transmitter of Fig. 4;
frequency and passes a current the direction and
l"lg.'7 is a diagram illustrating the operation
magnitude of which is determined by the varia
of the receiver of Fig. 6;
tion in signal frequency. One example of such
Figs. 8 and 9 are diagrams illustrating a novel
a discriminator is shown in Figure 1. The pri
form of variometer for usein the receiver of Fig.
mary circuit contains the coil 25 shunted by the
6; and
condenser 20, which can be adjusted to the beat
Figs. 10 and 11 are schematic diagrams illus
frequency. The secondary circuit contains a
trating further embodiments of the invention.
In Fig. 1, 10 is the oscillator valve of the trans 40 corresponding coil 31, shunted by a condenser
30. In addition to the inductive coupling of the
mitter. In the anode circuit of the oscillator
two circuits a further coupling is provided by
valve there is included a coil ii, which is induc
connecting the mid point 0! the coil 31 through
tively coupled to a coil i2 connected in the grid
circuit of the valve Ill, and to a further coil I!
connected by a transmission channel II to the
receiver. The coil i2 is connected in parallel with
a tuning condenser il, mechanically connected
to the transmitter control P, shown in the form of
a condenser 38 to the high voltage side relative
to alternating current, of the coil 25.
‘
The discriminator is completed by two recti
ilers l0 and 4|, connected to earth and to the
ends of the coil 31 and provided with the shunt
resistors 42, 48 and series resistors 44 and 45.
a dial. The resonance frequency of the tuned
circuit formed by the coil i2 and the condenser 50 For alternating currents the latter resistors are
shunted by by-pass condensers l6 and 41. The
M will thus vary with the position of the dial.
connection between the resistors 44 and 45 thus
The circuit l2-H is connected by a grid con
is connected to earth while the end terminals of
denser ii and a grid leak it to the grid circuit
these resistors are connected by conductors l8
of the valve ill to form an oscillating circuit.
The principal parts of the receiver are a modu 55 and 49 to the grids of direct current amplifying
,2
2,320,996
electronic valves 50 and 51, respectively.
The
0-D of the vectors O--A and O——B. As a result
one of the rectifiers 40 or H, for example the rec
anode circuits of the valves 50 and 5| are con
ti?er 40, receives a higher voltage and the voltage
balance between the load resistors of the recti
fiers is destroyed. With a greater voltage drop
‘nected in series with counteracting ?eld windings
l2 and 53 of the motor 2| to one terminal of
the armature 54 of the motor. the other terminal
across the load resistor 44 the grid voltage of the
valve 5!) falls and the anode voltage of this valve
of which is connected to the plus terminal of the
mains. The shaft of the motor is connected to
the tuning condenser 33 and also to the object
also fails.
Simultaneously the voltage drop
across the load resistor 45 decreases so that the
S to be controlled, shown in the form of a dial.
The operation of this system is as follows:
grid voltage of the valve 5| rises and the anode
current of this valve also rises. Unequal cur
To start with it will be assumed that the trans:\
rents flow through the windings 52 and 53 and the
motor 54 turns in for example counter-clockwise
mitter is tuned to a predetermined position on the “
dial P. A frequency dependent upon the position
of the control dial P is transmitted through the
conductors ll to the modulator grid 21 of a valve
ll of the receiver. The oscillator is assumed to
direction.
-
'
-
I
The motor 54 thus changes the‘setting of the
oscillator condenser 33 and gradually brings this
to‘ a value such that the beat frequency is restored
to theifrequency to which the circuits 35—-36 and
3'I—38 are tuned.
In these earlier proposed arrangements, how
20
> circuits 35-36 and 3l—-38 are tuned.
ever, certain disadvantages are present. For
In Fig. 2' the voltage vector of the circuit 35-36
example, the transmitter condenser can only vary
, is indicated by O-A. The voltage vector of they
from minimum value to maximum value repre
circuit 31-38 is indicated by B-C. ‘It is well
known that at absolute. resonance the voltage - senting for normal condensers a mechanical
vectors of the primary circuit and of the second 25 range of variation of half a revolution. Often.
however, this is not sufficient for obtaining the
ary circuit are exactly 90° out of phase relatively
desired range of movement or su?icient precision
to one another. Due to the coupling through the
in the receiver. In such cases it is desirable to
condenser 39 the voltage O-A is added to half
make the arrangement capable of operating in
the voltage 3-0 in positive direction for applica
tion to the recti?er l0, and in negative direction 30 such'a way that the control means of the trans
mitter can be turned more than half a revolution,
for application to the rectifier ll. The former
in many cases even a plurality of revolutions, the
voltage is thus composed of the vectors O--A and
controlled means of‘ the receiver thereby turning
0-0, while the latter voltage is composed of the
a corresponding number of revolutions. This is,
vectors O-A and O—B. As will be seen from
however, as explained below, impossible with an .
the diagram in Fig. 2 the two resultants O--D and
arrangement of the kind shown above.
0-13 in this case are equal. Consequently both
The capacity of a tuning condenser varies dur
recti?ers 40 and ll set- up equal but counter-act
ing one revolution between a maximum through a
ing voltages over their load resistors, which after
minimum and back to the same maximum value.
ampli?cation in the electronic valves 50 and ii
For each revolution of the shaft of the condenser
are transmitted to the two windings 52 and 53 of
such a cycle of capacity variation is obtained, as
the motor 2 I. The latter is consequently in
shown in Fig. 3 in which the vertical axis repre
balance and does not operate.
sents the capacity and the horizontal axis reprea
It will now be assumed that the setting of the
sents the angular setting of the condenser. It
transmitter is changed. The condenser I4 is thus
may now be assumed that the arrangement is set
shifted and the transmitter frequency is changed
in a position corresponding to point 55 in Fig. 3
either to a higher or to a lower value. The?beat
and that a movement is begun from this position
frequency will therefor differ from its normal
in the direction indicated by the arrow 56. The
value either in the same direction as the trans
mitter frequency or in the opposite direction, 0 change in transmitted frequency produces a cor
responding change in its beat frequency which
dependent on whether the frequency of the oscil
thus increases or decreases, dependent upon
lator'tuning circuit 22 is above or below the trans
whether the oscillator frequency is above‘ or below
mitter frequency. The direction in which the
the signal frequency. The change in frequency
beat frequency deviates is of no importance as
set up an oscillation of a frequency which [com
blues with the frequency received from the trans
mitter to produce the beat frequency to which the
regards the operation, as in every case the direc
tion, is dependent upon the direction of’ deviation
of the transmitter frequency. The beat frequency,
however, after the position of the dial P has been
changed, is no longer in exact resonance with the
55 causes an unbalanced voltage to be set up across
the two rectiflers, and as a consequence of this
, voltage the motor is started. The direction of
movement of the motor, however, is determined l
circuits 35-36 and 31-33. _,Hence the two vectors
O—A and B—C will assume a mutual phase posi
tion other than perpendicular to one another, and
shifted by an angle depending upon whether the
frequency displacement has been inductive or
capacitive. With‘reference to the diagram this 65
may ‘-be most easily explained by assuming that
one of the vectors, for example the vector O-A,
has turned relative to the other vector 3-0 as
indicated by the vector O-A’. As will be seen
by relation between the beat frequency and the
discriminator frequency. It may now be assumed
that the oscillator frequency is higher than the
signal frequency. The capacity, rising from the
point 55, will then cause a decreasing signal fre
quency, which will cause an increasing beat fre
quency and the motor is rotated in a direction to
restore the original beat frequency.
After the condenser ll of the transmitter has I
passed its maximum, represented by point 51 in
Fig. 3, the capacity will again decrease, thereby
‘ from Figure 2 this causes the resultant O—E' of 70 causing an increasing signal frequency. The
beat frequency decreases to the value to which
the vector O.—A’ and of the vector 0-0 to
become greater than the former resultant O-—E
of the vectors O--A and O—C, whereas on the
other hand the resultant 0-D’ of the vectors
O-A' and O—-B become less than the resultant 75
the discriminator is tuned, and thereafter the
beat frequency will remain lower than the dis
criminator frequency until the condenser M has
again ‘reached a reversal point, in this case the
3
2,320,996
minimum point 58. During this period the mo
tor in the receiver will continuously rotate in the
opposite direction until it reaches its end posi
tion. Hence, if the condenser ll should be turned
a plurality of revolutions the receiver would
follow the movement of the transmitter during
the ?rst half revolution only, rapidly moving back
mean value when the capacity of the other con
denser is a minimum or maximum.
,
The capacity variation oi‘; the two condensers
is shown in Fig. 5, the vertical axis as in Fig. 3
indicating the capacity and the horizontal axis
indicating the angular setting of the condenser.
The curve ll, drawn in full, shows the variation
of the capacity of one of the condensers whereas
to its initial position during the second half revo
the dotted curve Ii shows the variation of the
lution of the transmitter, following the trans
in the other condenser.
mitter during its third half revolution, again rap 10 capacity
A receiver for the signal emanating from the
idly returning to the initial position, etc.
transmitter in Fig. 4, is shown in Fig. 6, said re
The present invention relates to an arrange
ceiver being in general substantially the same as
ment by which this disadvantage is obviated.
the receiver, shown in Fig. l.’ The transmission
According to the invention the discriminator is
mains are indicated at ‘I! as in Fig. 4. Other
arranged in such a way that the control voltage ~
wise the same reference numerals have been used
for the remote control motor reverses its direc
as in Fig. 1 except that in the two parts of the
tion as the capacity curve of the condenser
receiver of Fig. 6, the hundreds-figures i and 2,
changes from rising to falling or vice versa. The
respectively, have been added.
reversal of the control voltage or current may
The transmission‘ mains ‘I! are connected to
take place either in the discriminator or in some 20 both of the receiver units through transformers
other place in the control channel. A number of
diflerent arrangements of this kind are shown
below.
At the moment when the control voltage or
current reverses its polarity thisvoltage or cur
rent will be zero. Hence, at the point of re
containing the primary windings I" and 265 and
blocking condensers I" and 256. The secondary
windings ill and 251 are broadly tuned by the
condensers I" and "I to the mean frequency
. of the received frequency band.
The condenser 33 in Fig. l is replaced in Fig.
6 by two condensers I59 and 25!,‘ and variable
condensers I“ and 2","respectively, coupled in
This disadvantage is obviated according to a fur
parallel. In the discriminators the inductive cou
ther embodiment of the invention by providing 30 pling is made variable by means of a variometea,
two cooperating transmitter units acting upon
For this purpose the primary and secondary cir
diii'erent receivers, the discriminators of which
cuits are screened from each other by means of I
are connected to the same remote control motor.
screens iii and 2H, respectively, and the primary
The condensers of both of said transmitters,
circuits are connected in series with the primary
however. are mechanically displaced in relation
coils I" and 2", respectively, of variometers, the
to each other in such a way that one of the con
secondary coils of which are formed by the sec
densers is in a position in which good precision
ondary coils I31 and, 23.1, respectively, of the dis- ‘
is obtained when the other condenser is in a po
criminator. Both of the variometers and both of
sition of less precision and vice versa.
the condensers are connected to a common me
Fig. 4 shows an arrangement of a transmitter 40
chanical control from the motor 54, as indicated
for two frequencies, intended to be connected to
by the dotted line II. This mechanical connec
versal the system loses its power of following the
movement of the transmitter with precision.
a receiver such as that shown in Fig. 6.
The transmitter according to Fig. 4 contains
two electronic valves 59 and 60, coupled as oscil
lators. The oscillation circuits contain one con
denser 6l or 62, respectively, and one coil 68 or
N, respectively. The cathodes of the electronic
valves are connected to taps on the respective
coils, whereas the high voltage terminals of the
coils are connected to the control grids of the
electronic valves over condensers 65 and it, pro
tion is made so that the variometers are at zero
coupling when the corresponding condensers pass
through their maximum or minimum positions.
In Fig. 5 this is indicated by the full line curve
ll corresponding to the capacity variation curve
80 of vthe condenser I60, and by the dotted curve
N which corresponds to the capacity variation
curve ll of the condenser 280.
By this arrangement an extremely uniform
movement of the receiver is obtained. Assuming
vided with grid leaks "and 88, respectively, in
that the variometers are moving with pure sine
a known manner.
variation in coupling, the polar curve for the
In the anode circuit of each of the valves 59
variation in coupling will be obtained in the form
and 60 is a broadly tuned circuit 89 and 10. re
of two circles touching each other. for example
spectively, said circuit transferring with substan
the circles I5 and II in Fig. '1 for one of the vari
tially the same amplitude all frequencies which
ometers and, due to the mechanical phase dis
may be set up by the oscillator valves. The cir
placement of 90°, the circles l1 and 8| for the
cuits are coupled to coils ‘H and ‘I2, respectively,
other variometer. The sum of ‘the coupling volt
which are connected by means of blocking con 60 ages through both of the variometers, which also
densers 13, ‘I4 to the transmission mains ‘I! lead
determines the current fed to the ?eld windings
ing to the receiver.
52 and 53 of the motor 54, is then obtained in
- The condensers ‘I and 62 are dimensioned in
Fig. 7 in form of the curve "- which varies only
relation to the coils ‘I and N to tune to a fre
quency which is not substantially higher than
the highest frequency which is to be produced by
the oscillator.
For obtaining a frequency varia
tion condensers ‘l6 and 11 are connected in paral
lel to the tuned circuits. These condensers are
mechanically connected with each other and with .
the transmitter control dial 1! as by a common
shaft 19. The stators of the two condensers ‘Hi
and 11 are displaced in relation to the rotors of
the said condensers in such a way that the capac
ity of one of the condensers is at or near. its
‘ about plus or minus 15% from a true circle as in
dicated by curve 90.
The operation of the variometers shown in Fig.
6 may cause certain di?iculties. as sliding con
tacts must be avoided due to the small voltages
involved, as well as due to the capacity of sliding
contacts which may be too high when the higher
radio frequencies are used for the control. In
Figs. 8 and 9 an arrangement is shown for ob
taining a variometer without using movable con
tacts. In these figures the coil of the primary
4
.
2,320,090
circuitin the discriminator is indicated at 9| and
the condenser coupled in parallel therewith is in_
dicated at 92.‘ In series with the coil 9| there is
and the secondary winding I63 of which is cou~
pled,in parallel with a condenser I64 for tuning
approximately to the mean value of the trans
arranged a coil 93. This coil is wound on a cylin
drical coil frame in the interior of which is ar
ranged a coaxial cylindrical coil frame carrying a
mitted frequency band. The signal is ampli?ed
coupling winding 94.
arranged on the same shaft as the primary wind
nected containing the primary winding I66 and
the secondary winding I61. The primary wind
ing 95 of the variometer, said last named wind- .
ing is coupled in parallel with a ?xed condenser
This coupling winding is
by means of a standard ampli?er valve I65 in
the output circuit of which a transformer is con
ing being so arranged that upon the‘ rotation of 10 I68 by means of which this circuit is tuned to a
frequency within the transmitted frequency
the variometer, a continuous and preferably pure
ly sinusoidal coupling variation to the secondary
. coil 96is obtained. As a matter of symmetry this
last named secondary coil is arranged with a mid
point tap and is connected between the two half
parts of the secondary winding 91 of the discrim
inator. The last named winding is ?nally coupled
in parallel with the condenser 98, corresponding
to the condensers I38 and 238, respectively. A
range. The secondary winding I61 is coupled in
parallel with a condenser I69 by means of which
said secondary winding is tunable over the same
frequency range as the transmitter. Preferably
the condenser I69 is so shaped that the receiver
during the automatic tuning always turns
through the same angle as the transmitter.
'
The coils I66 and I61 are connected as de
condenser 99 connects the mid-point on the sec 20 scribed above by means of a condenser I10 for
obtaining the discriminator action. The termi
ondary winding 96 with the primary winding 9|.
nals of the coil I 61 are connected to recti?ers I1I
In Figs. 10 and 11 two modi?cations of the ar
rangement according to Fig. 6 are shown. In - and I12 whichiare connected to load resistors
I13 and I14.
The connection point between the
the arrangement according to Fig. 6 the two di
rect current amplifying electronic valves I50 and
two load resistors is grounded, whereas the two
.I5I and also 250 and 25I, respectively, were so
ungrounded terminals are connected to the con
connected to the ?eld windings 52 and 53 of/the
trol grids of two direct current ampli?er valves
I15 and I16 by means of two contact arms I11
and I18. The counter contacts forthe contact
motor 54, that the sum of the currents ?owing
through the anode circuits of the electronic valves
in question passed through the ?eld windings. 30 arms are so arranged that. the contact arms,
which are mechanically connected together, when
At balance'between these currents no movement
in one position connect the resistor I13 with the
of the motor was obtained as the two ?eld wind
ampli?er valve I15 and the resistor I14 with the
ings were opposed. The arrangement according
ampli?er valve I16 but when in their other posi
to Fig. 10, however, is such that the difference
tion connect the resistor I13 with the ampli?er
between the voltages created in the two recti?ers
valve I16 and the resistor I14 with the ampli?er
is fed-to the ?eld windings. In this case the di
valve I15. The anode current from the valve
rect current amplifying electronic valves can be
n5 flows through the ?eld winding I19 01' the‘
omitted as will be evident from the following.
motor I80, whereas the’ anode current from the
The coupling from the transmitter to the two
modulator valves I00 and MI is assumed to be 40 valve I16 flows through the ?eld winding I8I.
The shaft I82 ‘of the motor I80 is coupled me
made in any manner suitable for the purpose,
chanically to actuate the tuning condenser I69 as
for example as shown in Fig. 6. The discrimina
well as the switching arms I11—I18, so that the
tors I02 and I03 are also made in a suitable man
arms are switched over from one position to the
ner. The discriminator I02 is connected to the
two recti?er valves I04 and I05, whereas the dis 45 other each time the condenser I69 passes through
maximum or minimum capacity positions. By
criminator I03 is connected to the two recti?er
this arrangement the receiver is prevented from
valves I06 and I01. The direct current voltages
reversing its direction at each half revolution of
from the recti?ers in question across the resist
the transmitter control as in'Fig. 1.
ors I00, I09, H0 and III are fed to four resistors
Of course the invention is not limited to the
H2, H3, H4 and H5, coupled in pairs. The con 50
nection point between the ‘resistors H2 and H4
embodiments shown. Various modi?cations may
be made therein as will be apparent to a person
and also between the resistors H3 and H5 are
skilled in the art.
connected to the control grids of ampli?er valves
What is claimed:
H6 and H1, respectively, provided with by-path
condensers H9 and‘ I20 and a common cathode 55 7 1. A remote control system responsive to fre
quency variations of a received signal, comprising
bias resistor I2I. The anode circuits are con
a receiver having a circuit responsive to the re
nected in the ?eld windings I48 and I49 of the
' ceived signal, arotatable tuning element pass
motor I22.
7
ing progressively through maximum and mini
In cases where a high precision is not required
this may be substantially simpli?ed. It is pri 60 mum positions during its rotation, said tuning
element being connected to control the frequency
marily possible to make the discriminator itself
response characteristics of said receiver, a re
tunable instead .of using a tunable oscillator cir
versible motor connected to actuate said tuning
cuit to obtain an intermediate frequency adapted
element, a motor control circuit responsive to the
to a ?xed discriminator. Further only one chan
nel may be used from the transmitter to the re 65 relative frequency characteristics of said receiver
and of the received signal and connected and ar
ceiver instead of two channels and ?nally it is not
ranged'to cause said tuning element to follow
necessary to make the reversal of the discrimina
variations in signal frequency, and a circuit con
tor voltage continuous, a mechanical switching
arrangement being used. An arrangement, sim
nected to cause said motor to continue operation
pli?ed in these three respects for receiving a re 70 in the same direction in response to continued
unidirectional variation in frequency of the re- ’
mote control signal is shown in Fig. 11.
ceived ‘signal as the tuning element passes
The transmission mains I1 from the trans
through its maximum or minimum position.
mitter, such as the transmitter shown in Fig. 1
are connected to a broadly tuned transformer,
' 2. A remote control system responsive to fre
the primary winding of which is indicated at I33 75 quency variations of a received signal, compris
4
2,320,996
ing a receiver having a circuit responsive to the
received signal, a rotatable tuning element pass
ing progressively through maximum and mini
mum positions during its rotation, said tuning
element being connected to control the frequency
5
response characteristics of said receiver, a re
versible motor connected to actuate said tuning
element, a motor control circuit responsive to the
relative frequency characteristics of said re
ceiver and of the received signal and connected
and arranged to cause said tuning element to fol
low variations in signal frequency, and reversing
connections comprising a variometer connected
response characteristics of said receiver, a revers
ible motor connected to actuated said tuning ele
ment, a motor control circuit responsive to the
and arranged to automatically reverse the con
relative frequency characteristics of said receiver
and of the received signal and connected and 10 trol of said motor control circuit as the tuning
control circuit passes through its maximum or
arranged to cause said tuning element to follow
minimum tuning position.
variations in signal frequency, and reversing con
6. A remote control system responsive to fre
nections connected and arranged to“\automati
quency variations of a received signal, compris
cally reverse the control of said motor control
ing a receiver having a circuit responsive to the
circuit as the tuning element passes through its
received signal, a rotatable tuning element pass
maximum or minimum position.
'
ing progressively through maximum and mini
3. A remote control system responsive to fre
mum positions during its rotation, said tuning
quency variations of a received signal, comprising
element being connected to control the frequency
a receiver having a circuit responsive to the re
ceived signal, a rotatable tuning element passing
progressively through maximum and minimum
positions during its rotation, said tuning element
being connected to control the frequency response
characteristics of said receiver, a reversible motor
connected to actuate said tuning element, a motor ~
response characteristics of said receiver, a re
versible motor connected to actuate said tuning
element, a motor control circuit responsive to
the relative frequency characteristics of said re
ceiver and of the received signal and connected
and arranged to cause said tuning element to
follow variations in signal frequency, said motor
control circuit comprising a pair of inductive
quency characteristics of said receiver and of the
coupling members connected in cascade, one of
received signal and connected and arranged to
said members comprising a variometer rotatable
cause said tuning element to follow variations in
with said tuning element, the other of said mem
signal frequency, and reversing connections actu 30 bers comprising coaxial coils the axis of which
ated by said tuning element and constructed and
coincides with the axis of rotation of said vari
arranged to automatically reverse the control of
ometer.
said motor control circuit as the tuning element
'7. A remote control system responsive to fre
passes through its maximum or minimum posi-,
quency variations of a pair of received signals
tion.
which are displaced in frequency and are varied
4. A remote control system responsive to fre
in frequency in the same sense, comprising a re
quency variations of a received signal, compris
ceiver having circuits selectively responsive to
ing a receiver having a circuit responsive to the
the two received signals, a pair of rotatable tun
received signal, a rotatable tuning element pass
ing elements passing progressively through maxi
ing progressively through maximum and mini 40 mum and minimum positions, said tuning ele
mum positions during its rotation, said tuning
ments being‘ mechanically connected to rotate in
element being connected to control the frequency
unison and relatively displaced as to their maxi
responsive characteristics of said receiver, a re
mum and minimum positions, said tuning ele
versible motor connected to actuate said tuning
ments being respectively connected to control
element, a motor control circuit responsive to
the frequency response characteristics of said
the relative frequency characteristics of said re
receiver circuits, a reversible motor connected
ceiver and of the received signal and connected
to actuate said tuning elements, a motor control
and arranged to cause said tuning element to
circuit responsive to the combined effect of the
follow variations in signal frequency, and revers
relative frequency characteristics of said receiver
ing connections connected and arranged to re
circuits and of the received signals and connect
verse the phase of a voltage component of the
ed and arranged to cause said tuning elements
motor control circuit so as to automatically re
to followv variations in their respective signal
verse the control of said motor control circuit
frequencies, said circuits being connected and
as the tuning element passes through its maxi
arranged to cause said motor to continue opera
mum or minimum position.
tion in response to variations in frequency of
5. A remote control system responsive to fre
one of said signals while the tuning element co
quency variations of a received signal, compris
operating with the circuit responsive to the other
ing a receiver having a circuit responsive to the
of said signals is passing through its maximum
received signal, a rotatable tuning element pass
or minimum position.
ing progressively through maximum and mini- 60
HARALD VALDEMAR ALEXANDERSSON.
mum positions during its rotation, said tuning
control circuit responsive to the relative fre
element being connected to control the frequency
CARL-ERIK GRANQVIST.