CABLE TELEVISION MONITORING SYSTEM

• US 3,769,579 A
• Filed: 03/31/1972
• Issued: 10/30/1973
• Est. Priority Date: 03/31/1972
• Status: Expired due to Term

• Current Assignee: OCI Communications, Inc. (AXXENT, Inc.)
• Original Assignee: Ralph Harney
• Inventors: Harney, Ralph
• Primary Examiner(s): Britton, Howard W.
• Application Number:
  US05/239,996
• Time in Patent Office: 578 Days
• Field of Search: 178/DIG.13 325/31,308 340/151
• US Class Current: 725/16
• CPC Class Codes: H04N 2007/17372 the upstream transmission being initiated or timed by a signal from upstream of the user terminal
• CPC Class Codes: H04N 7/087 with signal insertion during the vertical blanking interval only
• CPC Class Codes: H04N 7/173 with two-way working, e.g. subscriber sending a programme selection signal

Abstract

A system for interrogating TV receivers connected to a common distribution system, for example a cable or the like, in which a start signal activates transponders at each of the TV receivers and a series of clock signals, transmitted during the vertical blanking interval of the TV signal, are used to determine the reply periods of the transponders.

Claims

1. A method of interrogating a plurality of TV receivers connected to a common program distribution system, with each receiver having a transponder for signaling a common location, including the steps of:

sending a start signal to a plurality of transponders over the distribution system, with the start signal providing no interruption to the TV programming and being unique in character, sending a series of clock signals during subsequent vertical blanking intervals of the TV signal, groups of transponders replying to the start signal between subsequent vertical blanking intervals as determined by the number of clock signals received by the individual transponders.

2. The method of claim 1 further characterized in that the start signal is sent during the vertical blanking interval of the TV signal.

3. The method of claim 1 further characterized by the step of generating independent clock signals at each of the transponders, said clock signals being generated in response to received vertical sync signals during the vertical blanking intervals.

4. The method of claim 1 further characterized by and including the step of coding the transponder reply to provide different types of information.

5. The method of claim 1 further characterized in that all of said transponders receive the initial start signal, with said transponders replying in predetermined groups, with all the transponders in each group replying after a given number of clock signals.

6. The method of claim 1 further characterized by the step of cancelling an interrogation at a transponder if the TV channel is changed after the interrogation and prior to reply.

7. The method of claim 1 further characterized by the step of preventing a reply from an interrogated transponder if the TV signal is not at a predetermined level.

8. The method of claim 1 further characterizeD by the step of preventing a reply from an interrogated transponder if there is an absence of vertical sync pulses in the TV signal.

9. The method of claim 1 further characterized in that the start signal consists of an absence of horizontal sync pulses for a predetermined period.

10. The method of claim 9 further characterized in that the start signal takes place during the vertical blanking interval.