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Claims  |
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We claim:
1. A system for enabling only the transmission of a carrier signal having
the lowest instantaneous noise transient level in the transmitted portion
of identical electrical carrier signals of substantially equal signal
strength having differing noise transients and transmitted synchronously
and simulataneously over separate channels, the existence of such noise
tansients being reflected by differences in the instantaneous magnitudes
between said carrier signals, said system comprising:
comparing means connectable to said channels for continuously comparing the
total instantaneous signal-plus-noise magnitude of said carrier signals,
and actuable in response to the existence of a noise transient in any of
said carrier signals for enabling only the transmission of the carrier
signal having the lowest instantaneous noise transient level.
2. The invention according to claim 1 wherein said comparing means
comprises:
first control means connectable to said channels for generating switching
signals indicative of the channel carrying the carrier signal having the
lowest instantaneous transient noise level; and
enabling means connected to said first control means, and actuable in
response to said switching signals to enable only the channel carrying the
signal having the lowest transient noise level to transmit the carrier
signal.
3. The invention according to claim 2 and further including:
low frequency mixing means connectable between said channels for mixing
equally into all of said channels all signal components having frequencies
below a predetermined frequency level.
4. The invention according to claim 2 wherein the system includes first and
second channels for transmitting said identical electrical carrier
signals, and said first control means comprises:
first rectifying means connectable to said first channel for generating
first rectified signals of one polarity corresponding to signals
transmitted by said first channel;
second rectifying means connectable to said second channel for generating
second rectified signals opposite in polarity to said first rectified
signals, and corresponding to signals transmitted by said second channel;
and
polarity determining means connected to said first and second rectifying
means, for combining said first and second rectified signals and for
determining the polarity of the combined rectified signals, and for
generating said switching signals according to said polarity.
5. The invention according to claim 4 wherein said first and second
rectifying means each comprises full wave rectifiers having opposite
polarities, for respectively producing pulsating wave forms opposite in
polarity corresponding to the signals transmitted by said first and second
signals.
6. The invention according to claim 4 and further including first and
second high pass filter means connected to said first and second
rectifying means respectively, for eliminating from transmission through
said first control means, signal transients having frequencies below a
predetermined level.
7. The invention according to claim 4 and further comprising threshold
means for establishing a threshold value corresponding to a predetermined
difference in noise level between the respective channels and for
preventing the generation of said switching signals when the absolute
magnitude of the difference between the combined rectified signals is less
than said threshold value.
8. The invention according to claim 2 wherein the channels include first
and second channels for transmitting said identical carrier signals, and
said first control means comprises:
first rectifying means connectable to said first channel for generating
first rectified signals of one polarity corresponding to signals
transmitted by said first channel;
second rectifying means connectable to said second channel for generating
second rectified signals opposite in polarity to said first rectified
signals, and corresponding to signals transmitted by said second channel;
interconnecting means for interconnecting said first and second channels,
for combining said first and second rectified signals to generate a net
signal having a polarity corresponding to the polarity of said first or
second rectified signal greatest in absolute value;
first differentiating means having first and second inlet terminals, the
first of said inlet terminals being connected to said first and second
rectifying means, and outlet terminal means;
second differentiating means having first and second inlet terminals, the
latter first and second inlet terminals corresponding to the first and
second inlet terminals of said first differentiating means but being
opposite in polarity to the terminals to which said inlet terminals of
said second differentiating means correspond; said first inlet terminal of
said second differentiating means being connected to said first and second
rectifying means, and outlet terminal means;
means for impressing a potential across each of said second inlet terminals
opposite in polarity to the polarity of the signal received by said
respective inlet terminals;
selecting means connected to the outlet terminal means of each of said
differentiating means and actuable for effecting actuation of said
comparing means; and
said first and second differentiating means respectively generating
actuation signals to actuate said selecting means when the net signal
generated by said interconnecting means is both of the same polarity as
the polarity impressed across the respective first inlet terminals of said
first or second differentiating means, and exceeds the potential impressed
across the respective second inlet terminals of said first or second
differentiating means.
9. The invention according to claim 8 wherein said selecting means is a
bistable multivibrator which assumes first or second stable states
according to the respective one of said first and second differentiating
means which generates said actuation signals, said bistable multivibrator
actuating said enabling means to enable one of the channels to transmit
the carrier signal according to the stable state assumed by said bistable
multivibrator.
10. The invention according to claim 1 and further including means for
equalizing the components of said signals having frequencies below a
predetermined low frequency, and
wherein said comparing means compares only noise transients in said carrier
signals above said predetermined low frequency.
11. The invention according to claim 10 wherein said equalizing means
comprises a low frequency mixer connectable between said channels, said
mixer including resistor means connectable in each of said channels, and
capacitor means interconnecting said resistor means.
12. The invention according to claim 1 and further including:
summing means connectable to said channels for receiving and combining the
respective carrier signals;
and wherein said comparing means comprises means connectable to said
channels and to said summing means, and actuable for enabling the one of
said channels and said summing means having the lowest transient noise
level to transmit the signal carried thereby, and for disabling the other
of said channels and said summing means from transmitting the signals
carried thereby.
13. The invention according to claim 12 wherein said comparing means
comprises first comparing means and second comparing means, said first
comparing means comprising:
first control means connectable to said channels for generating first
switching signals indicative of the channel carrying the carrier signal
having the lowest transient noise level; and
first enabling means connected to said first control means, and actuable in
response to said first switching signals to enable only the channel having
the lowest transient noise level to transmit the carrier signal;
and said second comparing means comprising:
second control means connected to said channels and to said summing means,
said second control means generating a second switching signal indicative
of which of either of said channels or of said summing means is carrying
the signal having the lowest transient noise level; and
second enabling means connected to said second control means and actuable
in response to said second switching signals to enable only the one of
said channels and said summing means carrying the signal having the lowest
transient noise level, to transmit such latter signal having the lowest
transient noise level.
14. The invention according to claim 1 and further including:
summing means connectable to said channels for receiving the respective
carrier signals and for generating a combined signal;
and wherein said comparing means is further connected to said summing
means, said comparing means enabling only the one of the channels carrying
the signal having the lowest transient noise level and of said summing
means, carrying the signal having the lowest transient noise level to
transmit the signal carried thereby.
15. The invention according to claim 14 wherein said comparing means
comprises:
first control means connectable to said channels for generating first
switching signals indicative of the channel carrying the carrier signal
having the lowest transient noise level;
first enabling means connected to said first control means, and actuable in
response to said first switching signals to enable only the channel having
the lowest transient noise level to transmit the carrier signal;
second control means connectable to said channels and to said summing
means, said second control means generating a second switching signal
indicative of the one of said channels and of said summing means carrying
the signal having the lowest transient noise level; and
second enabling means connected to said second control means, and actuable
in response to said second switching signals to enable only the one of
said channels and of said summing means carrying the signal having the
lowest transient noise level, to transmit such latter signal having the
lowest transient noise level.
16. The invention according to claim 15 wherein the system includes first
and second channels for transmitting said identical electrical carrier
signals; and
said second control means comprises:
first rectifying means connectable to said first channel for generating
first rectified signals of one polarity corresponding to signals
transmitted by said first channel; and
second rectifying means connectable to said second channel for generating
second rectified signals having the same polarity as said first rectified
signals, and corresponding to signals transmitted by said second channel;
third rectifying means connected to said summing means for generating third
rectified signals opposite in polarity to said first and second rectified
signals, and corresponding to the combined signal generated by said
summing means;
first polarity determining means for combining said first and third
rectified signals and for determining the polarity of the combined first
and third rectified signals, and for generating a first switching signal
indicative of the one of said first channel and of said summing means
carrying the signal having the lowest transient noise level; and
second polarity determining means for combining said second and third
rectified signals and for determining the polarity of the combined second
and third signals, and for generating a second switching signal indicative
of the one of said second channel and of said summing means carrying the
signal having the lowest transient noise level;
and wherein said comparing means further comprises third enabling means
connected to said second control means for enabling the system to transmit
only the carrier signal having the lowest transient noise level as
determined by said first control means when said first switching signal
and said second switching signal indicate that the signal carried by
either of said first and second channels has a lower transient noise level
than said combined signal, and for enabling the system to transmit only
said combined signal when said first switching signal and said second
switching signal indicate that said combined signal has a lower transient
noise level than the signal carried by either of said first and second
channels.
17. The invention according to claim 16 wherein said first and second
polarity determining means each further include threshold means for
establishing a threshold value and for preventing the generation of said
first or said second switching signals when the absolute magnitude of the
difference between said respective combined rectified signals is less than
said threshold value.
18. The invention according to claim 14 wherein said comparing means
comprises:
first control means connectable to said channels and actuable for
generating first switching signals indicative of the channel carrying the
carrier signal having the lowest transient noise level;
first enabling means connectable to said first control means, and actuable
in response to said first switching signals to enable only the channel
having the lowest transient noise level to transmit the carrier signal;
second control means connectable to said channels and to said summing
means, said second control means generating a channel switching signal
when any one of said channels is carrying a carrier signal having a lower
transient noise level than the noise transient level in the combined
signal, and a summing switching signal when said summing means is carrying
a combined signal having a noise transient level lower than the noise
transient level on any of said carrier signals at a corresponding time;
outlet means for transmitting an output signal from the system;
second enabling means connected to said second control means and actuable
in response to signals generated by said second control means for
selectively enabling only the channel carrying the carrier signal having
the lowest transient noise level as indicated by said first control means
to transmit such carrier signal to said outlet means in response to said
channel switching signal, and for selectively enabling only said summing
means to transmit the combined signal to said outlet means in response to
said summing switching signal.
19. The invention according to claim 18 wherein said system includes first
and second channels, and said second control means comprises:
means for comparing the carrier signals carried by each of said channels
with said combined signal, and for generating signals indicating whether
the carrier signal carried by either of said channels has a transient
noise level lower than the transient noise level of the combined signal;
and a bistable multivibrator for generating said channel switching signal
when one of said channels is carrying a carrier signal having a lower
transient noise level, and for generating said summing switching signal
when the combined signal has a lower transient noise level than either of
said carrier signals.
20. The invention according to claim 1 wherein a pair of said channels each
include amplifying means for amplifying the respective carrier signals on
the channels, and wherein said system further includes balance control
means for balancing the respective carrier signal voltages on the pair of
channels, said balance control means comprising:
imbalance sensor means for monitoring the carrier signal voltages in the
respective channels, and for generating imbalance signals in response to
the sensing of an imbalance in the magnitude of the voltages of the
respective monitored carrier signal voltage; and
gain adjusting means connected to said imbalance sensor means and to at
least one of said amplifiers to adjust the respective gains of said at
least one amplifiers in response to the reception of said imbalance
signals.
21. The invention according to claim 20 and further including:
first rectifying means connectable to a first one of said pair of channels
for generating first rectified signals of one polarity corresponding to
signals transmitted by said first channel;
second rectifying means connectable to a second one of said pair of
channels for generating second rectified signals opposite in polarity to
said first rectified signals, and corresponding to signals transmitted by
said second channel; and
combining means for combining said first and second rectified signals, to
generate a net signal having a polarity corresponding to the polarity of
the one of said first or second rectified signal greatest in absolute
value and an electric potential corresponding to the net electric
potential of said combined signals;
and wherein said imbalance sensor means comprises an electric lamp
electrically connected to said net signal generating means for emitting a
gain control illumination signal proportionate in intensity to the value
of said net signal;
and wherein said gain adjusting means comprises photosensitive gain control
means electrically connected to at least one of said amplifier means for
adjusting said amplifier means in response to said gain control
illumination signal, to adjust the gains of said amplifier means towards
an equal value.
22. The invention according to claim 21 wherein said balance control means
further comprises low pass filter means for filtering from said carrier
signals those signal components having frequencies above a predetermined
value corresponding to the frequency of noise transients in said carrier
signals.
23. The invention according to claim 1 wherein said comparing means
comprises:
first control means connectable to said channels for generating switching
signals indicative of the channel carrying the carrier signal having the
lowest transient noise level; and
first enabling means connected to said first control means, and actuable in
response to said switching signal to enable only the one channel carrying
the signal having the lowest transient noise level to transmit the carrier
signal; and
wherein said system further comprises:
blanking means connectable to said one channel for blanking a predetermined
portion of the carrier signal transmitted by said one channel;
second enabling means electrically connected to said blanking means and
actuable for selectively enabling said blanking means to perform the
blanking function;
second control means electrically connected to said second enabling means
and to said one channel for detecting noise transients in the carrier
signal transmitted by said one channel, and for generating actuating
signals to actuate said second enabling means in response to the detection
of a noise transient.
24. The invention according to claim 1 wherein said comparing means
comprises:
first control means connectable to said channels for generating switching
signals indicative of the presence of a noise transient having an
amplitude above a predetermined value in the carrier signal; and
first enabling means connected to said first control means, and actuable in
response to said switching signal to enable only the one channel carrying
the signal having the lowest transient noise level to transmit the carrier
signal; and
wherein said system further comprises:
blanking means connected to said channels for blanking a predetermined
portion of the carrier signal transmitted by said one channel;
second enabling means electrically connected to said blanking means and
actuable for selectively enabling said blanking means to perform the
blanking function;
second control means electrically connectable to said channels for
detecting noise transients in the carrier signal transmitted by said one
channel, and for generating blanking control signals in response to the
detection of a noise transient;
third control means electrically connected to said second enabling means
and actuable for actuating said second enabling means;
fourth control means electrically connected to said first, second and third
control means, for actuating said third control means in response to the
simultaneous occurrence of said switching signals and said blanking
control signals.
25. The invention according to claim 24 wherein said fourth control means
further includes means for actuating said third control means in response
to the occurrence of either said switching signals or said blanking
control signals.
26. A system for reducing the noise transients in a carrier signal
transmitted over a channel, said system comprising:
blanking means for blanking a predetermined portion of the carrier signals;
enabling means electrically connected to said blanking means and actuable
for selectively disabling said blanking means from performing the blanking
function or for enabling said blanking means to perform the blanking
function; and
control means electrically connectable to said channel for detecting noise
transients in said carrier signal and to said enabling means, said control
means comparing the instantaneous signal-plus-noise in said carrier signal
with a predetermined value which is a function of said signal and
detecting a noise transient when the instantaneous magnitude of said
carrier signal exceeds said predetermined value, for generating actuating
signals to actuate said enabling means to perform the blanking function in
response to the detection of a noise transient.
27. The invention according to claim 26 wherein said control means
comprises:
instantaneous voltage generation means for transmitting a first signal
reflective of the instantaneous voltage of the carrier signal;
peak voltage generation means for generating and transmitting a second
signal reflective of the average peak voltage of said first signal over a
predetermined time period;
differentiating means electrically connected to said instantaneous voltage
generation means and to said peak voltage generation means, for generating
a noise indicator signal when said first signal exceeds said second signal
to indicate the occurrence of a noise transient;
reference means for establishing a predetermined threshold voltage;
comparing means electrically connected to said differentiating means and to
said reference means for generating a blanking signal when said noise
indicator signal voltage exceeds said predetermined threshold voltage; and
means for connecting said comparing means to said enabling means, for
actuating said enabling means in response to said blanking signal.
28. The invention according to claim 27 and further comprising:
blanking signal control means electrically connected to said comparing
means for generating a switching signal for a predetermined blanking
period in response to said blanking signal, said blanking signal control
means being electrically connected to said enabling means for actuating
said enabling means for said blanking period in response to the occurrence
of said switching signal.
29. The invention according to claim 28 and further comprising:
disabling means electrically connected between said blanking signal control
means and said peak voltage generation means, for disabling said peak
voltage generation means from generating and transmitting said second
signal for said blanking period, in response to the generation of said
blanking signal.
30. The invention according to claim 29 and further comprising:
second disabling means electrically connected to said blanking signal
control means for disabling said blanking signal control means from
generating one of said switching signals for a predetermined length of
time, in response to the commencement of said blanking period.
31. The invention according to claim 28 wherein said enabling means
comprises:
switch means electrically connected to said blanking signal control means
and to said blanking means, and actuable from a deactive condition in
response to the occurrence of a blanking signal to enable said blanking
means to perform the blanking function; and
delay means electrically connected to said switch means and to said
blanking signal control means for impeding the deactivation of said switch
means from the actuating condition after termination of a switching signal
generated by said blanking signal control means, whereby said blanking
function terminates gradually after the termination of said switching
signal.
32. The invention according to claim 31 wherein said delay means comprises:
variable resistor means connected across said switch means, and having a
normally high resistance; and
resistance control means for decreasing the resistance of said variable
resistor means to a low value during a switching signal from said blanking
signal control means, and for gradually increasing the resistance of said
variable resistor means after termination of the switching signal.
33. The invention according to claim 32 wherein said variable resistor
means comprises photoresistor means whose resistance is inversely
proportionate to the intensity of illumination, and a light source
energizable by said blanking signal control means in response to a
blanking signal, for illuminating said photoresistor during the blanking
period, said illumination gradually decreasing upon termination of the
blanking period.
34. The invention according to claim 26 wherein system has input and output
terminals and said enabling means comprises:
a first electrical path between said input and output terminals, said
blanking means being in said first electrical path;
first switching means for connecting said blanking means to said output
terminal in response to the generation of an actuation signal by said
control means;
differentiating means connected to said blanking means for generating a
differential signal corresponding to the voltage difference across said
blanking means;
sample and hold means connected between said differentiating means and said
output terminal;
second switching means actuable for connecting said differentiating means
to said sample and hold means in response to the generation of an
actuation signal by said control means, said sample and hold means
charging to the value of said differential signal in response to the
actuation of said second switching means;
said first and second switching means disconnecting said blanking means and
said differentiating means from said output terminal in response to
termination of said actuation signal, and said sample and hold means
gradually discharging an output signal to said output terminal in response
to the disconnection of said sample and hold means from said
differentiating means gradually to terminate the effect on the carrier
signal by said blanking function.
35. The invention according to claim 34 wherein said sample and hold means
comprises parallel connected capacitance means and resistor means.
36. The invention according to claim 26 wherein said control means is
further connected to said blanking means, and said control means commences
the generation of actuating signals in response to the detection of said
noise transients, and said control means terminates the generation of an
actuating signal after both a predetermined period after the commencement
of a detected noise transient, and after the instantaneous signal voltage
difference across said blanking means becomes below a predetermined value.
37. The invention according to claim 36 wherein said control means
comprises:
instantaneous voltage transmission means for transmitting a first signal
reflective of the instantaneous voltage of the carrier signal;
peak voltage generation means for generating and transmitting a second
signal reflective of the average peak voltage of said first signal over a
predetermined time period;
differentiating means electrically connected to said instantaneous voltage
generation means and to said peak voltage generation means, for generating
a noise indicator signal when said first signal exceeds said second signal
to indicate the occurrence of a noise transient;
threshold voltage means for establishing a predetermined voltage;
comparing means electrically connected to said differentiating means and to
said threshold means, for generating a blanking signal when the voltage of
said noise indicator signal exceeds said threshold voltage;
blanking signal control means electrically connected to said comparing
means for generating a switching signal for a predetermined blanking
period in response to said blanking signal, said blanking signal control
means being electrically connected to said enabling means for actuating
said enabling means for said blanking period in response to the occurrence
of said switching signal;
blanking termination means electrically connected to said blanking means
and to said blanking signal control means and to said enabling means, for
deactivating said enabling means a predetermined perod of time after the
generation of a particular control signal and when the instantaneous
voltage drop across said blanking means is below a predetermined low
voltage level, whereby the deactivation of said enabling means has no
audible effect.
38. The invention according to claim 37 wherein said blanking termination
means comprises:
differentiating means connected to said blanking means for generating a
blanking means voltage drop signal reflective of the voltage drop across
said blanking means;
means for establishing said predetermined low voltage level;
voltage drop comparing means connected to said differentiating means and to
said means for establishing said predetermined low voltage level, for
comparing said voltage drop signal with said predetermined low voltage
level, said voltage drop comparing means generating a low difference
signal when the difference between said voltage drop signal and said
predetermined low voltage level is less than a predetermined amount; and
bistable multivibrator means connected to said voltage drop comparing means
and to said blanking signal control means, for deactivating said enabling
means in response to the termination of said switching signal and to said
low difference signal.
39. The invention according to claim 26 wherein said control means
comprises:
threshold determining means electrically connectable to said channel for
generating blanking command signals when the amplitude of the carrier
signal exceeds a predetermined threshold value corresponding to the
amplitude of a noise transient;
blanking signal control means electrically connected to said threshold
determining means for actuating said enabling means in response to a
blanking command signal;
timing means electrically connected to said threshold determining means for
measuring the repetition rate of individual blanking command signals, and
for generating a de-activation signal when the repetition rate of
individual command signals is less than a certain amount in a first
predetermined time period corresponding to the dur | | |
