Bidirectional digital signal transmission system and repeater for the same

• US 6,345,390 B1
• Filed: 06/17/1997
• Issued: 02/05/2002
• Est. Priority Date: 12/28/1993
• Status: Expired due to Fees

• Current Assignee: Hitachi Denshi Kabushiki Kaisha
• Original Assignee: Hitachi Denshi Kabushiki Kaisha
• Inventors: Eto, Yoshizumi, Murata, Nobuo
• Primary Examiner(s): Miller, John W.
• Application Number:
  US08/877,560
• Time in Patent Office: 1,694 Days
• Field of Search: 725/105, 725/127, 348/211, 348/212, 348/722, 348/14.01, 348/14.05, 348/14.08, 348/14.1, 348/14.11, 348/14.12, 348/14.13, 370/259, 370/260, 370/263, 370/293, 370/433, 370/458, 370/521
• US Class Current: 725/127
• CPC Class Codes: H04N 23/66 Remote control of cameras or camera parts, e.g. by remote control devices
• CPC Class Codes: H04N 7/141 between two video terminals, e.g. videophone telephonic communication systems combined with television receiver for reception of entertainment or information matter H04M11/085
• CPC Class Codes: H04N 7/142 Constructional details of the terminal equipment, e.g. arrangements of the camera and the display
• CPC Class Codes: H04N 7/147 Communication arrangements, e.g. identifying the communication as a video-communication, intermediate storage of the signals selecting H04Q
• CPC Class Codes: H04N 7/181 for receiving images from a plurality of remote sources

Abstract

A bidirectional digital signal transmission system includes a transmission line, and video instruments respectively connected to both ends of the transmission line. In each of the video instruments, a digitized signal is multiplexed on a time division basis and compressed in a time base, thereby generating a transmission signal constituted by repetition of a signal period and a quiescent period. The transmission signal generated by one of the video instruments is transmitted during the quiescent period of the transmission signal generated by another one of the video instruments, thereby realizing bidirectional digital signal transmission. The system further includes a repeater circuit inserted in the transmission line at an intermediate location thereof to compensate for deterioration of the signal occurring during transmission over the transmission line. The repeater circuit includes a switch device for preventing a transmission signal feedback loop from being formed in the repeater circuit.

Claims

1. A bidirectional digital signal transmission system including a transmission line and video instruments connected to said transmission line at both ends thereof, respectively, wherein in each of said video instruments, a digitized signal is multiplexed on a time division basis and compressed in a time base, whereby a transmission signal constituted by repetition of a signal period and a quiescent period is generated, said transmission signal generated by one of said video instruments is transmitted during the quiescent period of the transmission signal generated by another one of said video instruments to thereby realize a bidirectional digital signal transmission, said system comprising:

a repeater circuit inserted in said transmission line at an intermediate location thereof for compensating for deterioration of the signal brought about during transmission by way of said transmission line;

wherein said repeater circuit includes switch means for preventing a transmission signal feedback loop from being formed in said repeater circuit.

2. A bidirectional digital signal transmission system according to claim 1,

one component of said transmission signal being a video signal having video data compressed,

wherein compression ratio of said video signal being adjusted in dependence on a transmission distance of said transmission line which in turn depends on a number of said repeater circuits as inserted, and

wherein a total sum of time periods during which the transmission signals of both of said video instruments do not concurrently exist on said transmission line is set at least equal to twice a delay time inherent to said transmission line.

3. A bidirectional digital signal transmission system according to claim 1, wherein the one of said video instruments is a television camera head unit, while the other one of said video instruments is a television camera control unit.

4. A bidirectional digital signal transmission system according to claim 1,

said switch means including a switch circuit for interrupting a signal path for a transmission signal from one of said video instruments.

5. A repeater apparatus for a bidirectional digital signal transmission system in which digital signals each containing video information and audio information are transmitted alternately from both ends of a transmission line periodically at a predetermined interval for allowing said digital signals to be transmitted and received, respectively, at both ends of said transmission line substantially on a real time basis,

said repeater apparatus being disposed on said transmission line and comprising:

a first compensation circuit for compensating for deterioration of a first digital signal transmitted from one end of said transmission line to the other end, said deterioration being brought about by said transmission line;

a second compensation circuit for compensating for deterioration of a second digital signal transmitted from said other end of said transmission line to said one end, said deterioration being brought about by said transmission line;

a control circuit for detecting at least one of said first digital signal and said second digital signal to thereby generate a control signal; and

switch means for opening/closing a signal path for one of said first compensation circuit and second compensation circuit in response to said control signal.

6. A repeater apparatus according to claim 5,

wherein each of said first and second digital signals contains a synchronizing signal,

said control circuit including:

means for detecting said synchronizing signal; and

counter means for measuring a predetermined time, starting from the detection of said synchronizing signal,

wherein said switch means interrupts the signal path for said first or second compensation circuit during a period corresponding to said predetermined time in response to said control signal.

7. A repeater apparatus according to claim 6,

wherein an input terminal of said first compensation circuit and an output terminal of said second compensation circuit are connected to one end of said transmission line, while an output terminal of said first compensation circuit and an input terminal of said second compensation circuit are connected to the other end of said transmission line,

said switch means including:

a first switch circuit capable of selectively opening and closing a connection path between the output terminal of said first compensation circuit and the other end of said transmission line; and

a second switch circuit capable of selectively opening and closing a connection path between the output terminal of said second compensation circuit and the one end of said transmission line.

8. A repeater apparatus according to claim 7,

wherein said control circuit generates a control signal for closing said first switch circuit upon detection of presence of a synchronizing signal in said first digital signal while generating a control signal for opening said first switch circuit unless said synchronizing signal of said first digital signal is detected, whereas upon detection of a synchronizing signal in said second digital signal, said control circuit generates a control signal for closing said second switch circuit while generating a control signal for opening said second switch circuit unless the synchronizing signal of said second digital signal is detected.

9. A repeater apparatus according to claim 7,

wherein said control circuit generates a control signal for closing said first switch circuit and opening said second switch circuit upon detection of presence of a synchronizing signal in said first digital signal while generating a control signal for opening said first switch circuit and closing said second switch circuit unless said synchronizing signal of said first digital signal is detected.

10. A repeater apparatus according to claim 7,

wherein said control circuit generates a control signal for closing said second switch circuit and opening said first switch circuit upon detection of presence of a synchronizing signal in said second digital signal while generating a control signal for opening said second switch circuit and closing said first switch circuit unless said synchronizing signal of said second digital signal is detected.

11. A repeater apparatus according to claim 7,

wherein each of said first compensation circuit and said second compensation circuit includes an equalizer for processing said first or second digital signal in accordance with predetermined values so that amplitude and pulse width thereof are restored close to those of the original digital signal.

12. A repeater apparatus according to claim 5,

said control circuit further comprising:

means for stopping operation of either one of said first and second compensating circuits in dependence on said control signal.