Local network forming part of a cable tv system

• US 20030084458A1
• Filed: 06/12/2002
• Published: 05/01/2003
• Est. Priority Date: 12/14/1999
• Status: Abandoned Application

• Current Assignee: Spacenet Proxilliant Systems AB
• Original Assignee: Spacenet Proxilliant Systems AB
• Inventors: Carlsson, Lars Ake Peter, Cullblom, Bo Peter, Ljungdahl, Kjell Arne
• Application Number:
  US10/149,382
• Publication Number:
  US 20030084458A1
• Time in Patent Office: Days
• US Class Current: 725/124
• CPC Class Codes: H04N 7/102 Circuits therefor, e.g. noise reducers, equalisers, amplifiers H04N7/108 takes precedence
• CPC Class Codes: H04N 7/17309 Transmission or handling of upstream communications

Abstract

A local network (10), forming part of a cable TV system, includes subscriber outlets (21), from which signals can be transmitted in the return direction to a head end (11) of the system within a predetermined carrier frequency band. The network (10) is provided with a noise reduction unit (23) comprising an input (24), connected to the subscriber outlets (21), an output (27), connected to the head end (11), a plurality of band-pass filters (28-31), connected to said input (24) and having mutually different pass bands lying within said carrier frequency band, and a corresponding plurality of detectors (32-35), which are arranged each to compare the energy level of the output signal from one of said filters (28-31) with at least one predetermined reference level and to deliver logic signals depending upon the result of said comparison to a logic control unit (36), which is arranged to determined whether these signals satisfy certain conditions stored in the control unit (36) and to deliver a control signal, depending hereupon, to a controllable blocking circuit (26), which is connected in a separate line (25), serving to transmit signals from said input (24) to said output (27), and which is arranged to permit signals to pass therethrough only when it receives a control signal from the control unit (36), indicating that the logic signals received by the control unit (36) satisfy the conditions stored in said unit.

Claims

1. Local network (10), forming part of a cable TV system and being arranged to permit a transmission of signals in the return direction from subscriber outlets (21) included in said network (10) to a head end (11) of said system within a predetermined carrier frequency band, serving for the transmission of signals in said direction, said network being provided with a noise reduction unit (23) serving to reduce the amount of noise transmitted in the return direction from said network (10) and comprising an input (24) connected to the subscriber outlets (21), an output (27) connected to the head end (11), a plurality of band-pass filters (28-31) connected to said input (24) and having mutually different pass bands lying within said carrier frequency band, a corresponding plurality of detectors (32-35), which are connected each to one of said filters (28-31) and which are arranged each to compare the energy level of the output signal from the respective filter (28-31) with at least one predetermined reference level, and blocking means (26), operatively connected to said detectors (32-35) and arranged to permit or prevent a transmission of signals from said input (24) to said output (27) in dependence upon the result of the comparison effected by said detectors (32-35), characterized in that, for at least one group of adjacent pass bands, said blocking means are formed by a single blocking circuit (26) which is common to all pass bands within said group and connected in a separate line (25), serving for the transmission of signals within these pass bands from said input (24) to said output (27), and which is operatively connected to each of the detectors (32-35) belonging to said group of pass bands.

2. Local network according to claim 1, characterized in that said group includes all pass bands within said carrier frequency band.

3. Local network according to claim 1 or 2, characterized in that the detectors (32-35) belonging to said group of pass bands are arranged to deliver logic output signals depending upon the comparison effected by them to a logic control unit (36) which is arranged to determine whether these signals satisfy certain conditions stored in the control unit (36) and to deliver a control signal, depending hereupon, to the blocking circuit (26), in order hereby to bring this circuit to permit a transmission of signals from said input (24) to said output (27) only when said output signals from the detectors (32-35) satisfy said conditions.

4. Local network according to claim 3, characterized in that said conditions consist of conditions permanently stored in the control unit (36).

5. Local network according to claim 3, characterized in that the control unit (36) is reprogrammable and arranged to permit an alteration of the conditions stored therein.

6. Local network according to any of the preceding claims, characterized in that at least one of the detectors (32-35) belonging to said group of pass bands is arranged to compare the energy level of the output signal from the band-pass filter (28-31) connected thereto with at least two different reference levels.

7. Local network according to claim 6, characterized in that the control unit (36) is arranged to determine the slope of the front edge of the output signal from the band-pass filter (28-31) connected to said at least one detector (32-35) and to ascertain whether it satisfies a corresponding condition stored in the control unit (36).

8. Local network according to claim 7, characterized in that the control unit (36) is arranged to deliver a signal for permitting a signal transmission through the blocking circuit (26) only on the condition that the value of the determined slope falls within a predetermined permitted interval.

9. Local network according to any of the preceding claims, characterized in that said at least one reference level or each of said reference levels, respectively, is adjustable.

10. Local network according to any of the preceding claims, characterized in that it includes a delay means (41) provided in the connection (25) between the input (24) of the noise reduction unit (23) and the blocking circuit (26).