U.S. patent number RE29,997 [Application Number 05/838,990] was granted by the patent office on 1979-05-15 for signal distribution device for a cable television.
This patent grant is currently assigned to Oak Holland, B.V.. Invention is credited to Pieter den Toonder.
United States Patent |
RE29,997 |
den Toonder |
May 15, 1979 |
**Please see images for:
( Certificate of Correction ) ** |
Signal distribution device for a cable television
Abstract
A cable television signal distribution system provides a
plurality of television programs and radio programs which are
transmitted in frequency multiplex to a plurality of subscriber
drop lines. A data receiver and logic control unit, after decoding
suitable supplied codes, control the operation of a plurality of
high frequency switches by which the received programs can be
switched and/or jammed from a remote locate to selectively provide
subscribers the desired program.
Inventors: |
den Toonder; Pieter (Dordrecht,
NL) |
Assignee: |
Oak Holland, B.V. (Emmen,
NL)
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Family
ID: |
26645069 |
Appl.
No.: |
05/838,990 |
Filed: |
October 3, 1977 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
581139 |
May 27, 1975 |
04039954 |
Aug 2, 1977 |
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Foreign Application Priority Data
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Dec 24, 1974 [NL] |
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7416880 |
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Current U.S.
Class: |
370/486; 370/489;
380/205; 380/240; 455/1; 455/3.04 |
Current CPC
Class: |
H04N
7/166 (20130101) |
Current International
Class: |
H04N
7/16 (20060101); H04B 001/06 () |
Field of
Search: |
;325/308,132,32,34
;179/15BD ;358/114,122 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Griffin; Robert L.
Assistant Examiner: Masinick; Michael A.
Attorney, Agent or Firm: Kinzer, Plyer, Dorn &
McEachran
Claims
I claim:
1. A signal distribution means for use with a cable television
network having a supply line in which a plurality of TV programs
are transmitted in frequency multiplex to a plurality of subscriber
drop lines, said means including a data receiver connected to the
supply line a logic control unit connected to said data receiver, a
plurality of high frequency switches controlled by said logic
control unit, and a jamming oscillator connected to each high
frequency switch, said high frequency switches responding to
control signals from said data receiver and logic control unit to
provide jamming signals from designated oscillators to said
subscriber drop lines to prevent clear reception of designated TV
programs.
2. The means of claim 1 further characterized by and including
attenuation means connected between each oscillator and its
associated high frequency switch.
3. The means of claim 1 further characterized in that each high
frequency switch includes three unidirectionally connected diodes,
the junctions on each side of the center diode being connected to
ground by the series combination of a diode and capacitor.
4. The means of claim 3 further characterized in that the cathode
of one series diode is connected to the cathode of the center diode
with the anode of the other series diode being connected to the
anode of the center diode.
5. The means of claim 4 further characterized by and including
capacitors connected to the cathode of the first of said three
unidirectionally directed diodes and to the anode of the third of
said three unidirectionally connected diodes.
6. The means of claim 5 further characterized by and including a
series resistive circuit shunting said center diode.
7. Signal distribution means for use with a cable television
network having a supply line on which a plurality of TV programs
are transmitted in frequency multiplex to a plurality of subscriber
drop lines, said means including a connection from the supply line
to each subscriber, a data receiver connected to the supply line, a
logic control unit connected to said data receiver, and a plurality
of high frequency switches controlled by said logic control unit,
each high frequency switch including a low frequency oscillator for
variably tuning said high frequency switch, said high frequency
switches responding to control signals from said data receiver and
logic control unit to prevent clear reception of designated
programs.
8. The means of claim 7 further characterized by and including a
jamming oscillator connected in series with each high frequency
switch.
9. The means of claim 7 further characterized in that each high
frequency switch includes a parallel circuit of an inductance and a
variable capacitance, said low frequency oscillator being connected
to said variable capacitance.
Description
The invention relates to a signal distribution device for a cable
television network having a supply line, by which a plurality of
television programs and radio programs are transmitted in frequency
multiplex to a plurality of subscriber drop lines. Such a signal
distribution device is known in practice.
In the known cable television networks subscribers are usually
connected with the aid of signal distribution devices to a supply
or ring line distributing in frequency-multiplex a plurality of
television programs and radio programs to the relevant subscribers.
A certain number of subscribers in such a system is connected to
each distribution device.
A disadvantage connected with said system, is that during the
installation of said cable television network only those
subscribers can be connected to the distribution devices, who
previously have indicated that they wanted to be connected to the
system. Upon a later subscription a technician has to connect the
residence of said subscriber to a related distribution device which
is costly and time-consuming. Upon both a termination and a
non-payment a technician has also to deconnect the subscriber from
the distribution device.
With the system indicated in the introduction it is therefore not
always possible to deny already connected subscribers the reception
of certain programs.
It is an object of the invention to supply a signal distribution
device, whereby already during the installation of the television
network each residence is connected to the distribution device,
such that by implementation of remote control with a suitable code
each subscriber from a central location can be connected at each
desired moment to the cable television network or can be
disconnected from said network.
It is also an object of the invention to allow the implementation
of said remote control with a suitable code such that certain
programs on certain subscriber drop lines can be jammed so that
observation and listening of the related program is made
impossible.
A signal distribution device according to the invention is
characterized by one or a plurality of high-frequency switches by
which said programs can be remotely switched and/or jammed, of
which switches for each subscriber line one is inserted in series
and/or a plurality is taken up in co-operation with this line; a
data receiver and a logic control unit which after decoding of the
suitable codes switches the series switch(es) for tansmission of
the high-frequency program signals and/or the switch(es)
cooperating with the line(s) for jamming of certain high-frequency
signals.
The distinct advantage in said system is that each subscriber
connected to the distribution device, can be connected or
disconnected from a central location and also that each subscriber
can be allowed or can be denied the reception of certain programs
without jamming of the other subscribers.
An additional advantage is also that a subscriber is not able to
switch on himself. The invention will be explained with the aid of
an embodiment with reference to the drawings, in which:
FIG. 1 is a block diagram of a signal distribution device including
four subscriber drop lines, whereby in each line a high-frequency
switch is inserted in series and whereby the transmission and the
disconnection respectively of the programs can be switched
remotely;
FIG. 2 is a block diagram of a signal distribution device including
a single subscriber drop line, provided with four high-frequency
switches co-operating in parallel with the line for jamming at wish
of certain television programs and radio programs;
FIG. 3a is a drawing of an embodiment of a high-frequency switch of
the semi-conductive type, which is used in the device according to
FIG. 2;
FIG. 3b is a drawing of the portion relative to the high-frequency
operation of the high-frequency switch according to FIG. 3a;
FIG. 4 is a front view of a housing in which the distribution
device is taken up
FIG. 5 is a block diagram of a signal distribution device including
a single subscriber drop line provided with four high-frequency
switches of another type inserted in series with the line for
jamming at wish of certain television programs and radio
programs;
FIG. 6 is a drawing of an embodiment of a high-frequency switch of
said other type, which is used in the device according to FIG. 5;
and
FIG. 7 is a drawing of another embodiment of a high-frequency
switch of said other type which singularly can be used for a
plurality of channels.
Referring to FIG. 1, there is shown a supply or ring line 1, a
plurality of subscriber drop lines 2, a data receiver 3, a logic
control unit 4, high-frequency switches 5 and a braching element 6.
The data receiver 3 in said distribution device is connected to the
branching- or coupling distribution point. For said branching
function a directional coupler or a tap can be used. The logic
control unit following the data receiver, decodes the suitable
codes introduced in the high-frequency signal. Depending upon the
information of said codes the control unit 4 will switch one or a
plurality of high-frequency switches 5 such that the high-frequency
signals of the related television programs and radio programs are
transmitted to the subscriber lines 2 or are blocked from
transmission.
Referring to FIG. 2, a block diagram is indicated of a signal
distribution device by which it is feasible to couple jamming
signals into the subscriber drop lines by which the related
subscribers can be allowed or can be denied the reception of
television programs and radio programs. Again referring to FIG. 2,
there is indicated a supply line 1, a single subscriber drop line
2, a data receiver 3 connected to the branching distribution point,
a logic control unit 4, a single high-frequency switch inserted on
series with the subscriber line 2. Also there is shown a plurality
of high-frequency switches 5 taken up in parallel with the
subscriber line 2, a plurality of preconnected oscillators 9 and a
plurality of attenuators 7 connected in between.
The oscillators 9 substantially have the same frequency as the
related programs, such that upon a closed switch 5 a strong
interference signal is introduced in the subscriber line to thereby
interdict the observation and listening of the program. As the
signal is coupled into the subscriber line, for these jamming
signals low levels, for example about O dBmV, can be used. These
jamming levels can be maintained with the aid of for example a
pin-diode attenuator, which is controlled by the automatic gain
control of the data receiver. In order to prevent leakage into the
system, the oscillator signals are introduced via a directional
coupler 8 into the subscriber line.
With reference to FIG. 3a, there is shown a high-frequency switch
of the semi-conductive or solid-state type. The attenuation of this
switch in the 50-300 MHz-region is better than 88 dB. The applied
power is 2 mA for 5 V direct current. The operation is as
follows:
If point A is positive with respect to point B, there will follow a
direct current in the circuit R.sub.1, D.sub.1, R.sub.2, R.sub.3,
D.sub.2, R.sub.4, by which the series diodes D.sub.3, D.sub.4 and
D.sub.5 are connected in reverse direction and the parallel diodes
D.sub.1 and D.sub.2 are connected in forward direction. With
reference to FIG. 3b, there is indicated with respect to the
high-frequency operation how the assembly constitutes an attenuator
comprising large series-impedances (D.sub.3, D.sub.4 and D.sub.5)
and small parallel-impedances (D.sub.1 with C.sub.1 and D.sub.2
with C.sub.2), such that the high-frequency signal is not
transmitted from the input to the output (and also not vice
versa).
If point A is negative with respect to point B, there will follow a
direct current in the circuit R.sub.6, D.sub.5, D.sub.4, D.sub.3,
R.sub.5, by which the series diodes D.sub.3, D.sub.4 and D.sub.5
are connected in forward direction and the parallel diodes D.sub.1
and D.sub.2 are connected in reverse direction. The high-frequency
signal now is transmitted practically without attenuation. The
capacitors C.sub.3 and C.sub.5 serve to block the DC voltage
applied to the points A and B, to the high-frequency cables.
The capacitor C.sub.3 is used in order to prevent the occurence of
a high-frequency leakage via R.sub.2 and R.sub.3 parallel to
D.sub.4 (in reverse direction). All resistors serve to set the DC
bias and they do not have a high-frequency function.
The high-frequency switch can also be of the mechanical type.
For four subscribers for a branching point by way of example the
following is requires:
- one data receiver;
- one logic unit including for the
branching address: n bits
subscriber address: 2 bits
connect/disconnect: 1 bit
four programs: 4 bits
- four oscillators and corresponding attenuators;
- four subscriber units each including five high-frequency
switches.
In principle, any number of subscribers and a number of programs
per unit can be combined.
Referring to FIG. 4 there is indicated how such a combination can
be inserted in a formed housing.
Referring to FIG. 5, there is indicated a block diagram of a signal
distribution device, with which it is possible as with the device
according to FIG. 2, to allow and to deny respectively the
subscriber the reception of four or more or less programs
respectively. The same componencts in FIG. 4 as those according to
FIG. 2 are indicated by the same reference numbers. Instead of four
high-frequency switches 5 in parallel with the subscriber line,
however, four high-frequency switches 10 of another type are
inserted in series with the line.
Referring to FIG. 6, there is indicated a drawing of the
high-frequency switch 10 of the other type. Before this switches of
said other type the high-frequency switch 5 (S.sub.1) can be
inserted in series for the transmission of blocking respectively of
all high-frequency program signals per subscriber. In the switch 10
a T-filter is inserted in series with the subscriber line, and a
parallel circuit of an inductance 11 and among others a Varicap 12
is inserted in the cross branch of the T-filter. By periodically
controlling said Varicap 12 with for example a low-frequency signal
of 50 or 1000 Hz, the tuning of the circuit can be swept across the
whole channel or a portion thereof, such that periodically (not
synchronously) always another, relatively small portion of the side
bands of the signal is filtered out so that the resulting signal is
jammed. The tuning of this high-frequency switch or trapping
circuit is obtained in the position "na" (not authorized) of the
switch S.sub.2 by adjusting the inudctance 11 on the channel to be
jammed. Care should be taken during this procedure that adjacent
program channels are not disturbed a bit either. By placing the
switch S.sub.2 under control of the control unit 4 from the
position na to the position "a" (authorized), the jamming of the
related program channel is removed. The switch S.sub.2 only
switches low frequencies and therefore can be both of the
mechanical type and of the solid-state type.
As the Varicap diode is switched in forward direction in the
position a, a current from the DC-voltage source flows via S.sub.2,
the resistor R, the Varicap 12 and the inductance 11 back to the
source. The inductance is short-circuited and the two capacitors C
having relatively small values, occur in parallel with the line and
then have practically no influence on the signal transmission.
It is also feasible to simultaneously jam a plurality of channels
being adjacent to each other, by selecting the low frequencies
sweep to be large enough. In this case one switch 10 for a
plurality of channels is sufficient.
Referring to FIG. 7 there is indicated how the switch 10 for
example can be tuned on four different channels by periodically
connecting this switch via a solid-state switch (S.sub.2 and
S.sub.3 -S.sub.6) to different negative voltages by which a
plurality of channels is subsequently jammed. The switch S.sub.2
can periodically (for examples 3 .mu. sec) be connected through. Of
the switches S.sub.3 -S.sub.6 for four programming channels each of
them under control of the control unit 4 can be adjusted to a
positive DC voltage only (no jamming) or to the low-frequency
voltage superimposed upon a negative DC-voltage.
The tuning is then determined by the DC voltage on the varicap and
the trapping circuit is swept with the 50 or 1000 Hz voltage across
the related channel. By connecting or disconnecting said
low-frequency voltages with the aid of the data receiver and the
control unit, program after program can be allowed or denied
respectively. Each channel which is denied, can be sufficiently
jammed in this way by the correct selection of the repetition
frequency.
In order to jam a plurality of channels a parallel connection,
besides the first mentioned series connection and the above
mentioned plural connections can also be used, namely by inserting
in the longitudinal branch of the T-filter a plurality of trapping
circuits parallel to each other.
* * * * *