Use Surveying Or Monitoring (e.g., Program Or Channel Watched) Patents (Class 725/9)
- By detecting local oscillator or IF signal (Class 725/15)
- By polling (Class 725/16)
- By monitoring sync or blanking pulse (Class 725/17)
- By use of audio signal (Class 725/18)
- By use of pattern recognition or signature (Class 725/19)
- By data encoded in video signal (e.g., VBI data) (Class 725/20)
- Combined with detecting VCR operation (Class 725/21)