JPS608675B2 - Signal splitter for cable television - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal distribution system for a television network having feed lines for transmitting a large number of television and radio programs in a frequency multiplexed manner to a large number of subscriber drops.

Such signal splitters are known in practice. In known cable television networks, subscribers are followed by a signal distributor on a feed line or ring line which supplies a large number of television and radio programs to the subscribers concerned in a frequency multiplexed manner.

In such systems, a fixed number of subscribers are also connected to each distributor. A disadvantage of said system is that during the installation of the cable television network only those subscribers who previously wanted to be attached to the system are attached to the distributor.

For subsequent subscribers, ``an engineer must move the subscriber's home to the associated distributor at an expensive and time-consuming cost. must remove the subscriber from the distributor.Thus, in conventional systems it is not always possible for an already connected subscriber to refuse to receive a certain program.

It is well known that pay television programs or radio programs are frequency-multiplexed and transmitted with general broadcast programs.

Furthermore, it is also a common form of broadcasting service to switch between general broadcasting and paid broadcasting by using a suitable video switch, and it is also known that such switching is performed using a control signal from the transmitting side. However, conventional systems of this type use fairly complex switching means,
It increases the system cost.

One object of the present invention is to provide a signal distribution system for connecting or disconnecting each subscriber and cable television at any time by remote control using appropriate codes (control data). 1 at the service line
The object of the present invention is to provide a signal distribution system, characterized in that each drop-in line is provided with at least one semiconductor-type high-frequency switch for interfering with the transmission of one or more designated channels.

Another object of the invention is that the high frequency switch provided in each service line is adapted to couple the jamming signal from the jamming oscillator to the service line through an attenuator controlled by the automatic gain control of the data receiver. An object of the present invention is to provide a signal distribution system characterized in that two signals are arranged in parallel.

One advantage of the system of the invention is that each subscriber connected to the distributor can be connected to a central location (
network (supply line), and allow or deny reception of any channel without interfering with other subscribers.

The above and other objects and advantages of the present invention will be clearly understood from the following description taken in conjunction with the accompanying drawings.
This is a block diagram of a signal distribution system including two subscriber drop-in lines, each of which has a high-frequency switch inserted in series.
Program transmission and disconnection switching is performed remotely.

In FIG. 1, a supply or ring line 1, a number of subscriber lines 2, a data receiver 3, a logic control unit 4, a high-frequency switch 5 and a branching element 6 are shown.

The data receiver 3 in the distributor is connected to a branch or combination distribution point 6. A directional coupler or tap is used as the branching element. A logic control unit 4 downstream of the data receiver 3 decodes the appropriate code conveyed in the high frequency signal. Depending on the code information, the control unit 4 switches one or more high-frequency switches 5 to block the transmission of the high-frequency signals of the relevant television and radio programs to the subscriber drop-in line 2. FIG. 2 shows a signal distribution system that facilitates coupling of jamming signals to subscriber drop-in lines, which jamming signals allow or deny reception of television and radio programs to the subscriber concerned.

FIG. 2 also shows a supply line 1, a single subscriber drop-in line 2,
A data receiver 3 connected to a distribution point 6, a logic control unit 4 and a single high frequency switch 5 inserted in series with the subscriber line 2 are shown. Furthermore, FIG. 2 shows a large number of high frequency switches 14 arranged in parallel with the subscriber line 2.
, a number of pre-connected oscillators 9 and a number of attenuators 7 connected between the high frequency switch 14 and the oscillators 9 are shown. The oscillator 9 has practically the same frequency as the program concerned, and by closing the switch 14,
A strong interfering signal is introduced into the subscriber line that prohibits viewing of the program.

Since the program signal is coupled to the subscriber line, a low level signal such as obBmV is used as the interfering signal. These interference levels are maintained by, for example, pin-diode attenuators controlled by automatic gain control of the data receiver. To prevent leakage to the system,
The oscillator signal is guided to the subscriber line via a directional coupler 8. FIG. 3a shows a semiconductor or solid state type high frequency switch used in the device of FIG.

The attenuation of this switch in the 50-300 MHz band is 8
Better than spot B.

The applied and discharged power is 2 hA for 5 V DC. The operation is as follows: If point A is positive with respect to point B, then R,...
Direct current flows through the circuits D,, R2, R3, D2, and R4,
Thereby, the series diodes D3, D4, D5 are connected in the reverse direction, and the parallel diodes D,, D2 are connected in the forward direction. FIG. 3b shows the large series impedances D3, D4, D5 and the small parallel impedances C. of the circuit of FIG. 3a. It shows how an attenuator consisting of and D, , C2 and D2 is configured in relation to high frequency operation, where high frequency signals are not transmitted from the input to the output and vice versa. is also not transmitted. If point A is negative with respect to point B, direct current flows through the circuit R6, D5, D4, D3, R5, thereby causing series diodes D3, D4
, D5 are connected in the normal direction, and the parallel diodes D,, D
2 are connected in the opposite direction.

Thus, high frequency signals are transmitted virtually without attenuation. Capacitors C4 and C5 block the DC voltage applied to points A and B from being applied to the high frequency cable. Capacitor C3 is used to prevent high frequencies from leaking in the opposite direction through R2 and R3, which are parallel to D4.

All the resistors are for DC bias and have no high frequency function. As an example, for 4 subscribers per branch, the following would be required: 1 1 logic unit containing 1 data receiver 2 branch address shelf n bits, 2 bits for subscriber archive, 1 bit for continuation or disconnection, 4 bits for 4 programs 3 4 oscillators and 4 Attenuator 4 Four subscriber units each containing five radio frequency switches In principle, a large number of subscribers and programs can be combined per unit.

FIG. 4 is a view of the front of the cliff body in which the distributor is housed.

FIG. 5 shows a block diagram of a signal distributor, similar to the system of FIG. 2, which can allow or deny each subscriber from receiving four or more or fewer programs. In Figure 4, elements that are the same as those in Figure 2 are given the same numbers. However, instead of four high-frequency switches 5 in parallel with the subscriber line, four high-frequency switches 10 of another type are inserted in series with the line. FIG. 6 shows an embodiment of the high frequency switch used in the device shown in FIG.

A high frequency switch S,
are inserted in series to block or transmit all high frequency program signals for each subscriber. In the switch 101, the T-type filter is inserted in series with the subscriber line, and the cross-branch portion (vertical limb) of the T-type filter has an inductance of 1
A parallel circuit of 1 and varicap 12 is inserted. By periodically controlling the varicap 12 with a low frequency signal of, for example, 50 or 1000 Hz, the tuning of the circuit is swept over all or some channels. Thus, periodically (rather than synchronously) in the sidebands of said low frequency signal, only another relatively small portion of the signal is disturbed such that the composite signal is disturbed.
Filtered and removed. Tuning of this high frequency switch or trumpet circuit is obtained by placing the switch S2 in the na (not common) position and adjusting the inductance 11 on the channel to be disturbed.

Care must be taken throughout this procedure to ensure that adjacent program channels do not interfere with each other in any way. Under the control of the control unit 4, by placing the switch S2 from the position na to the position a (which is typical), the disturbance for the associated program channel is shifted. Switch S2 only switches low frequencies and therefore can be either a mechanical switch or a solid state switch. Since the varicap diode is switched in the forward direction at position a, the current from the DC voltage source 15 flows through S2, resistor R,
It passes through the varicap 12 and the inductance 11 and returns to the power source 15.

The inductance is short-circuited, and the two capacitors C of considerably 4.0 cm are placed in parallel with the subscriber line 2 and have virtually no effect on the signal transmission. By choosing the low frequency sweep of the frequency source 16 to be large enough, it is possible to simultaneously jam a large number of channels that are close to each other.

In this case, one switch 10 is sufficient for a large number of channels. FIG. 7 shows an embodiment of a high frequency switch used in the device of FIG. It is shown how by periodically connecting switch 10 one can tune to four different channels.

Switch S2 is connected periodically (eg every 3 French seconds). Switch S for 4 programs and channels to be created
3 to S6 are controlled by the control unit 4 and operate only with a positive DC voltage (no interference) or with a low frequency voltage superimposed on a negative DC voltage.

The tuning is determined by the DC voltage of the varicap, and the trap circuit connects or disconnects said low frequency voltage by means of a data receiver and a control unit, which are swept at 50 or 1000 voltage between the channels concerned, and each program is received separately. is accepted or rejected.

By choosing the repetition frequency correctly, the rejected channels will be sufficiently blocked.

In order to disturb a large number of channels, in addition to the series connection described at the beginning and the multiple connections mentioned above, parallel connections are used. This parallel connection allows a large number of channels to be jammed by inserting a large number of trap circuits in parallel with each other at the vertical branches of the T-type filter.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a signal distribution system including four subscriber drop lines, and FIG. 2 is a block diagram of a signal distribution system including a single subscriber drop line.
The block diagram of the two signal distribution systems, FIG.
Figure 3b is a diagram showing a portion of the high frequency switch shown in Figure 3a that is related to high frequency operation, and Figure 4 is a diagram showing an example of a semiconductor high frequency switch used in the device. The front view of the body, FIG. 5, is a block diagram of a signal distributor comprising a single subscriber drop-in line with four high-frequency switches of other types inserted in series with the line, FIG.
FIG. 5 is a diagram of an embodiment of a high frequency switch used in the apparatus, and FIG. 7 is a diagram of an embodiment of a high frequency switch used singly for multiple channels. DESCRIPTION OF SYMBOLS 1... Supply line, 2... Subscriber drop-in line, 3... Data receiver, 4... Logic control unit, 5... High frequency switch, 10... High frequency switch, 12... Bali cap diode. Hakama. Z force 9.2. Tan, Monomi, Hiroshi. Domain. 〆． Way. J S. 6 Hiiragi. vinegar

Claims (1)

Claims: 1 Used in a cable network having a supply line 1; for transmitting a plurality of television and/or radio channels together with control data in a frequency multiplexed manner to a plurality of subscriber lines 2; comprising a data receiver 3 connected;
A signal comprising a logic control device connected to the data receiver 3 to demodulate the control data and to control one high frequency switch 5 connected in series with each drop-in line 2 to turn the drop-in line 2 on or off. In the distribution system, each drop line 2 is provided with at least one solid state radio frequency switch 14, 10 which is actuated by said control data and which interrupts the transmission of one or more designated channels in the drop line 2.
A signal distribution system characterized by being provided in. 2 Said high frequency switch 14 provided in each drop-in line 2 is configured to couple the disturbance signal from the jamming oscillator 9 to said drop-in line 2 via an attenuator 7 controlled by the automatic gain control of said data receiver 3. 2. The signal distribution system according to claim 1, characterized in that the signal distribution system is arranged in parallel with two. 3. The high-frequency switches 5, 14 are configured as a diode-resistor-capacitor network for high-frequency operation, including a series circuit consisting of three diodes D_3, D_4, D_5 connected in the same direction; The connection points are grounded through series circuits D_1, C_1 and D_2, C_2 consisting of diodes and capacitors; the cathode D_1 of one diode D_1
is connected to the cathode of the central diode D_4, and the anode of the other diode D_2 is connected to the anode of the central diode D_4. Signal distribution system. 4 The high frequency inputs and outputs of the high frequency switches 5, 14 are connected to the cathode of the first diode D_3 and the anode of the third diode D_5 via capacitors C_4, C_5, respectively; the central diode D_4 is connected to two resistors connected in series. The connection point between these resistors is grounded through a capacitor C_3; the series circuit of diodes D_3 and D_1 and the diode D_5
, D_2 consists of two resistors R_5 connected in series.
, R_1 and R_6, R_4, and the connection points A and B between these resistors are connected to a DC voltage. 5 Said high frequency switch 10 provided on each drop line 2 is arranged in series with said drop line 2 to filter out a certain channel; and said high frequency switch 10 is provided in T
It is constructed as a type filter, the crossed limbs of which are provided with an inductance 11 and a varicap 12; said varicap 12 is periodically controlled via a switch S_2 by a low-frequency signal superimposed on the negative DC voltage or The signal distribution system according to claim 1, characterized in that it is connected to a direct current voltage. 6. The variable cap 12 of the crossed limb of the high frequency switch 10 is connected to a plurality of other switches S_3 to S_6 via the switch S_2;
has the same number of switch positions as the plurality of switches S_3 to S_6, and is periodically connected to the switches S_3 to S_6 via these switch positions;
Selected positions of _3 to S_6 are connected to a positive DC voltage or to a low frequency signal superimposed on another negative voltage,
6. Signal distribution system according to claim 5, characterized in that all or part of the channels are thereby disturbed.