System and method for inductive line synchronization

• US 7,218,356 B2
• Filed: 11/22/2005
• Issued: 05/15/2007
• Est. Priority Date: 04/02/2001
• Status: Expired due to Term

• Current Assignee: Pelco Incorporated (Motorola Solutions, Inc.)
• Original Assignee: Pelco (Schneider Electric SE)
• Inventors: Rowe, David
• Primary Examiner(s): Ometz; David
• Assistant Examiner(s): DESIR, JEAN WICEL
• Application Number:
  US11/285,000
• Publication Number:
  US 20060077257A1
• Time in Patent Office: 539 Days
• Field of Search: 348/521, 348/536, 348/537, 348/730, 348/518, 348/516, 348/153, 348/139, 348/222.1, 348/14.11, 348/705, 348/706, 348/495, 348/143, 348/159, 345/213, 345/212, 315/276, 315/266, 315/254, 327/86, 327/190, 333/119, 323/215, 323/355
• US Class Current: 348/521
• CPC Class Codes: H04N 5/0733 for distributing synchronisation pulses to different TV cameras

Abstract

A synchronization signal generating apparatus and method in which an input circuit is inductively coupled to an alternating current signal line. The input circuit generates a rectified signal. A switch has a switch input and a switch output in which the switch input is electrically connected to the input circuit and is enabled when the voltage of the rectified signal is greater than a predetermined voltage and is disabled when the rectified signal voltage is less than the predetermined voltage. A pulse generating circuit has a pulse generating circuit input and a pulse generating circuit output. The pulse generating circuit input is electrically connected to the switch output. The pulse generating circuit generates a pulse each time the switch is enabled. The synchronization signal generating apparatus is used in a synchronized television display system to signal a video switch to switch the video signal generated by a camera to a monitor based on the occurrence of the synchronization signal.

Claims

1. A synchronized television display system comprising:

a plurality of cameras generating video signals;

a monitor for displaying a video signal generated by one of said plurality of cameras;

a video selection unit electrically connected to said plurality of cameras and said monitor, for connecting a selected camera from said plurality of cameras to said monitor;

an AC line having an AC signal; and

a synchronization unit comprising an AC line sensing device comprising a core and a coil wrapped around said core for generating a signal corresponding to the AC signal on said AC line and a synchronization circuit connected to said AC line sensing device for providing a synchronization signal to said video selection unit, wherein said AC line is wrapped around said AC line sensing device and said AC line sensing device is not electrically connected to said AC line and said video selection unit switches the video signal generated by a selected camera from said plurality of cameras to said monitor based on the occurrence of the synchronization signal.

2. The synchronized television display system according to claim 1, wherein the video selection unit further includes a central processing unit electronically coupled to the synchronization circuit, the central processing unit receiving the synchronization signal and causing the video signal generated by the selected camera to be switched to the monitor.

3. The synchronized television display system according to claim 2, wherein the central processing unit generates a display authorization signal based at least in part on the receipt of the synchronization signal.

4. The synchronized television display system according to claim 3, wherein the video selection unit further includes a switch matrix in electrical communication with the central processing unit, the plurality of cameras and the monitor the switch matrix electrically coupling the video signal from the selected camera to the monitor upon receipt of the display authorization signal from the central processing unit.

5. The synchronized television display system according to claim 3, wherein the central processing unit executes programmatic code which performs the function of causing the video switch to provide the monitor with a video signal from a camera determined in accordance with previously stored switching instructions, the switching instructions including at least one display time duration for which the monitor will display the video signal for a corresponding camera, wherein the central processing unit generates the display authorization signal upon the expiration of a display time duration and upon receipt of the synchronization signal.

6. The synchronized television display system according to claim 3, wherein the synchronization signal is provided to the central processing unit as an interrupt signal.

7. A synchronized television display system as recited in claim 1, wherein said synchronization circuit comprises a rectifier connected to said AC line sensing device to rectify the signal from said AC line sensing device, a switch connected to said rectifier, said switch being enabled when the signal from said rectifier is greater than a predetermined level and disabled when the signal from said rectifier is less than the predetermined level, and a pulse generating circuit connected to said switch, said pulse generating circuit generating the synchronization signal each time said switch is enabled.

8. A synchronized television display system as recited in claim 1, wherein said synchronization unit is adapted to generate a synchronization signal corresponding to a phase of the AC line signal.

9. A synchronized television display system as recited in claim 1, wherein said video selection unit switches the video signal generated by a selected camera from said plurality of cameras to said monitor during a vertical blanking interval of said monitor.

10. A synchronized television display system as recited in claim 1, wherein said AC line has two lines and only one of said two lines is wrapped round said AC line sensing device.

11. A synchronized television display system as recited in claim 10, wherein said one AC line that is wrapped around said AC line sensing device is wrapped around the core of said AC line sensing device.

12. A synchronized television display system as recited in claim 11, wherein said core is a toroidal core.

13. A synchronized television display system as recited in claim 1, wherein said AC line sensing device is not a transformer.

14. A synchronized television display system as recited in claim 1, wherein said AC line sensing device is a coil.

15. A synchronized television display system comprising:

a plurality of cameras generating video signals;

a monitor for displaying a video signal generated by one of said plurality of cameras;

a video selection unit electrically connected to said plurality of cameras and said monitor, for connecting a selected camera from said plurality of cameras to said monitor;

an AC line having an AC signal;

a synchronization circuit comprising a toroidal transformer having a core, primary winding, and secondary winding, said AC line being wrapped around said core but not being electrically connected to said primary winding or said secondary winding, said toroidal transformer providing a synchronization signal based on said AC signal and said video selection unit switches the video signal generated by a selected camera from said plurality of cameras to said monitor based on the occurrence of the synchronization signal.

16. The synchronized television display system according to claim 15, wherein the video selection unit further includes a central processing unit electronically coupled to the synchronization circuit, the central processing unit receiving the synchronization signal and causing the video signal generated by the selected camera to be switched to the monitor.

17. The synchronized television display system according to claim 16, wherein the central processing unit generates a display authorization signal based at least in part on the receipt of the synchronization signal.

18. The synchronized television display system according to claim 17, wherein the video selection unit further includes a switch matrix in electrical communication with the central processing unit, the plurality of cameras and the monitor the switch matrix electrically coupling the video signal from the selected camera to the monitor upon receipt of the display authorization signal from the central processing unit.

19. The synchronized television display system according to claim 17, wherein the central processing unit executes programmatic code which performs the function of causing the video switch to provide the monitor with a video signal from a camera determined in accordance with previously stored switching instructions, the switching instructions including at least one display time duration for which the monitor will display the video signal for a corresponding camera, wherein the central processing unit generates the display authorization signal upon the expiration of a display time duration and upon receipt of the synchronization signal.

20. The synchronized television display system according to claim 17, wherein the synchronization signal is provided to the central processing unit as an interrupt signal.

21. A synchronized television display system as recited in claim 15, wherein said synchronization circuit comprises a rectifier connected to said AC line sensing device to rectify the signal from said AC line sensing device, a switch connected to said rectifier, said switch being enabled when the signal from said rectifier is greater than a predetermined level and disabled when the signal from said rectifier is less than the predetermined level, and a pulse generating circuit connected to said switch, said pulse generating circuit generating the synchronization signal each time said switch is enabled.

22. A synchronized television display system as recited in claim 15, wherein said synchronization unit is adapted to generate a synchronization signal corresponding to a phase of the AC line signal.

23. A synchronized television display system as recited in claim 15, wherein said video selection unit switches the video signal generated by a selected camera from said plurality of cameras to said monitor during a vertical blanking interval of said monitor.