CCTV system using multiplexed signals to reduce required cables

• US 5,623,304 A
• Filed: 09/23/1994
• Issued: 04/22/1997
• Est. Priority Date: 09/28/1989
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Matsumoto, Hajime, Ota, Kazuo, Soma, Satoshi, Kimura, Takayuki
• Primary Examiner(s): Tran, Thai Q.
• Assistant Examiner(s): LIN, BRYAN T
• Application Number:
  US08/311,702
• Time in Patent Office: 942 Days
• Field of Search: 358/108, 358/86, 455/3, 455/5, 455/6, 348/143, 348/152, 348/153, 348/154, 348/155, 348/156, 348/159, 348/212, 348/476, 348/478, 348/512, 348/518, 348/6, 348/8, 348/484, 348/485, 348/705
• US Class Current: 348/143
• CPC Class Codes: H04N 7/087 with signal insertion during the vertical blanking interval only
• CPC Class Codes: H04N 7/18 Closed-circuit television [CCTV] systems, i.e. systems in which the video signal is not broadcast

Abstract

A cable-saving type CCTV system for transmitting a multiplexed video signal over a single coaxial cable connecting a camera site and a control site by frequency-modulating a bi-directional audio signal and producing a digital control signal and a digital alarm signal and multiplexing the resultant signals and an external synchronizing signal in a blanking period of the video signal.

Claims

1. A closed circuit television system comprising:

(a) a single cable for transmitting signals;

(b) camera-site equipment, connected to said cable, comprising;

an external sync signal separation circuit for receiving a first composite signal through said cable and extracting an external sync signal from said first composite signal, and

a video camera for providing a video composite signal in the NTSC television standard onto said cable;

(c) at least one control-site means, operatively associated with said camera-site equipment through said cable, comprising;

input means for inputting a digital control signal for controlling said camera-site equipment,

means for generating and outputting said external sync signal which is used to synchronize operation of said video camera with another video camera,

first audio signal control means for (i) receiving a first audio signal inputted externally and outputting a first frequency modulated audio signal based thereon in a first modulated frequency band and (ii) receiving a second composite signal transmitted over said cable and demodulating a second frequency modulated audio signal from said second composite signal, and

first multiplex means for multiplexing said external sync signal, said control signal and said first frequency modulated audio signal to form said first composite signal and outputting said first composite signal onto said cable, wherein said control signal is placed in and transmitted in a first predetermined time area of a vertical blanking period of said video signal transmitted through said cable and said external sync signal is placed and transmitted in a second predetermined time area of said vertical blanking period of said video signal transmitted through said cable;

(d) signal processing means, operatively associated with said camera-site equipment and said control-site means through said cable, comprising;

alarm interface means for receiving a digital alarm signal inputted externally which is to be transmitted to said control-site means,

second audio signal control means for (i) receiving a second audio signal and outputting said second frequency modulated signal in a second modulated frequency band and (ii) receiving said first composite signal from said control-site means and demodulating said first frequency modulated audio signal from said first composite signal,

means for receiving said first composite signal, detecting said digital control signal and generating a confirmation signal, in response to said digital control signal, to confirm that said control signal has been properly received, and

second multiplex means for receiving said video signal transmitted through said cable and adding said alarm signal, said confirmation signal and said second frequency modulated audio signal to said video signal to form said second composite signal to be transmitted to said control-site means, wherein said alarm signal is superposed on said video signal in a third predetermined time area of said vertical blanking period of said video signal and said confirmation signal is superposed on said video signal in a fourth predetermined time area of said vertical blanking period of said video signal.

2. A closed circuit television system according to claim 1, wherein said input means comprises a keyboard.

3. A closed circuit television system according to claim 1, wherein said first audio signal control means comprises a frequency modulation modem having a carrier frequency higher than an original frequency band of said video signal.

4. A closed circuit television system according to claim 1, wherein said second audio signal control means comprises a frequency modulation modem.

5. A closed circuit television system according to claim 4, wherein said first audio signal control means comprises a frequency modulation modem, and a carrier frequency of said frequency modulation modem of said camera-site equipment is different from a carrier frequency of said frequency modulation modem of said first audio signal control means.

6. A closed circuit television system comprising:

camera site equipment having at least one video camera for generating a video composite signal in the NTSC standard;

at least one control-site means including means for generating an external sync signal for synchronizing operation of said video camera with another control-site means, control means for producing a digital control signal to control said video camera, and audio input/output means including an FM modem for modulating/demodulating an audio signal; and

a single cable connecting said camera site equipment and said at least one control-site means to transmit therethrough and therebetween the video signal in the NTSC standard generated by said camera;

wherein;

said camera site equipment comprises means for receiving a first composite signal, detecting said digital control signal and generating a confirmation signal, in response to said digital control signal, to confirm that said digital control signal has been properly received and transmitting through said cable said confirmation signal in a first predetermined time area of a vertical blanking period of the transmitted video signal in the NTSC standard, and

said control means transmits through said cable said generated external sync signal in a second predetermined time area of said vertical blanking period and said digital control signal in a third predetermined time area of said vertical blanking period and transmits through said cable said audio signal modulated by said FM modem.

7. A closed circuit television system comprising:

camera site equipment having at least one video camera for generating a video signal in the NTSC standard;

at least one control-site means including means for generating an external sync signal for synchronizing operation of said video camera with another camera, control means for producing a digital control signal to control said video camera, and audio input/output means including an FM modem for modulating/demodulating an audio signal; and

a single cable for operatively connecting said camera-site equipment and said control-site means to transmit therethrough and therebetween the video signal in the NTSC standard generated by said camera;

wherein;

said camera site equipment comprises means for receiving a first composite signal, detecting said digital control signal and generating a confirmation signal, in response to said digital control signal, to confirm that said digital control signal has been properly received and transmitting through said cable said confirmation signal in a first predetermined time area of a vertical blanking period of the transmitted video signal in the NTSC standard, and

said control means transmits through said cable said generated external sync signal in a second predetermined time area of said vertical blanking period and said digital control signal in a third predetermined time area of said vertical blanking period and transmits through said cable said audio signal modulated by said FM modem.

8. A closed circuit television system comprising:

camera site equipment having at least one video camera for generating a video signal in the NTSC standard;

a plurality of control-site means each including means for generating an external sync signal for synchronizing operations of said plurality of control-site means, control means for producing a digital control signal to control said video camera, and audio input/output means including an FM modem for modulating/demodulating an audio signal; and

a single cable for operatively connecting said video camera and said plurality of control-site means to transmit therethrough and therebetween the video signal in the NTSC standard generated by said video camera;

wherein;

said camera site equipment comprises means for receiving a first composite signal, detecting said digital control signal and generating a confirmation signal, in response to said digital control signal, to confirm that said digital control signal has been properly received and transmitting through said cable said confirmation signal in a first predetermined time area of a vertical blanking period of the transmitted video signal in the NTSC standard,

said control means transmits through said cable said generated external sync signal in a second predetermined time area of said vertical blanking period and said digital control signal in a third predetermined time area of said vertical blanking period and transmits through said cable said audio signal modulated by said FM modem, and

each of said control-site means includes means for receiving said confirmation signal.

9. A closed circuit television system comprising:

camera-site equipment having a plurality of video cameras each for generating a video signal in the NTSC standard;

a plurality of control-site means each including (i) means for generating an external sync signal for synchronizing operations of said video cameras, (ii) control means for producing a digital control signal to control at least one of said video cameras, and (iii) audio input/output means including an FM modem for modulating/demodulating an audio signal; and

a single cable for operatively connecting said plurality of cameras of said camera-site equipment and said plurality of control-site means, said cable for transmitting therethrough and therebetween the respective video signals in the NTSC standard generated by each of said cameras;

wherein said camera site equipment comprises means for receiving a first composite signal, detecting said digital control signal and generating a confirmation signal, in response to said digital control signal, to confirm that said digital control signal has been properly received and transmitting through said cable said confirmation signal in a first predetermined time area of a vertical blanking period,

each of said control means transmits, through said cable, its respective external sync signal in a second predetermined time area of said vertical blanking period and its respective digital control signal in a third predetermined time area of said vertical blanking period, and transmits, through said cable, said audio signal modulated by the FM modem associated with said each of said control means, and

each of said control-site means includes means for receiving said confirmation signal.

10. A closed circuit television system comprising:

camera-site equipment having at least one video camera for generating a video signal in the NTSC standard;

at least one control-site means including control means for producing a control signal to control said video camera and audio input/output means including an FM modem for modulating/demodulating an audio signal; and

a single cable for operatively connecting said camera-site equipment and said control-site means to transmit therethrough and therebetween the video signal in the NTSC standard generated by said camera;

wherein;

said camera site equipment comprises means for receiving a first composite signal, detecting said digital control signal and generating a confirmation signal, in response to said control signal, to confirm that said control signal has been properly received and transmitting through said cable said confirmation signal in a first predetermined time area of a vertical blanking period, and

said control means produces a composite video signal by multiplexing said control signal in a second predetermined time area of said blanking period of the video signal in the NTSC standard transmitted through said cable to provide a resultant multiplexed video signal and by multiplexing said resultant multiplexed video signal with said audio signal modulated by said FM modem to produce said composite video signal for transmission through said cable between said control-site means and said camera-site equipment.