COMMUNICATION INCLUDING SUBMERGED IDENTIFICATION SIGNAL

• US 3,845,391 A
• Filed: 07/15/1971
• Issued: 10/29/1974
• Est. Priority Date: 07/08/1969
• Status: Expired due to Term

• Current Assignee: Audicom Corporation
• Original Assignee: Murray G. Crosby
• Inventors: Crosby, Murray G.
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US05/162,774
• Time in Patent Office: 1,202 Days
• Field of Search: 179/2,2TC,3,1.2R 325/31,51,52,64,55,66,392,396,311,37 178/5.6 343/225-228
• US Class Current: 455/39
• CPC Class Codes: H04H 20/14 for monitoring programmes
• CPC Class Codes: H04H 20/31 using in-band signals, e.g. subsonic or cue signal
• CPC Class Codes: H04H 60/37 for identifying segments of broadcast information, e.g. scenes or extracting programme ID
• CPC Class Codes: H04H 60/58 of audio determination or detection of speech characteristics in general G10L25/00; speech recognition in general G10L15/00
• CPC Class Codes: H04N 7/081 the additional information signals being transmitted by means of a subcarrier

Abstract

A technique for identifying a program with an identification code in which the code is modulated onto an audio frequency subcarrier and transmitted with the program. A short time period, narrow band width window is cut out of the program material to accommodate the code carrying modulated audio subcarrier. The amount by which the code modulates the subcarrier is made to track with the audio envelope of the program and thus minimizes the listener'"'"''"'"'s ability to hear the code. The receiver equipment automatically responds to the presence of the subcarrier and detects the code. Unmodulated subcarrier is transmitted immediately prior to the code modulation to assure that there is no ambiguity between the code signal and program material. Automatic frequency control responsive to the unmodulated subcarrier compensates for tape or disc recorder speed variation. The automatic frequency control is disabled during the actual code transmission to prevent a receiver response that might wipe out the code signal.

Claims

1. The system for encoding transmitted audio program material comprising:

encoding means for generating a substantially inaudible, audio frequency code signal, the frequency band width occupied by said code signal being within the frequency band width of the audio program signal and being at least a decade in magnitude less than the frequency band width of the audio program signal, said code signal having an initial portion and an identification code portion, said initial portion having a predetermined time duration sufficiently great to provide substantial distinction between said initial portion and the audio program material signal, said identification code portion having at least one parameter with a value distinct from the value of the corresponding parameter of said initial portion, first timIng means coupled to said encoding means to limit the duration of said code signal to a first predetermined time period, first generating means in said encoding means for generating said initial portion of said code signal, second generating means in said encoding means for generating said identification code portion of said code signal, second timing means coupled to said second generating means for initiating the generation of said identification code portion after said initial portion has been generated for a second predetermined time period, said second predetermined time period being less that said first predetermined time period, and means transmitting said audio frequency code signal simultaneously with the transmission of the associated transmitted audio program material.

2. The system of claim 1 further comprising:

modulation means responsive to the amplitude of an envelope of the said program material signal to modulate the amplitude of said code signal as a function of the amplitude of the program material signal to provide a modulated code signal having a substantially lower amplitude at low audio program material signal levels than at high audio program material signal levels.

3. The system of claim 1 further comprising:

means to angle modulate said code signal on a subcarrier, the initial portion of said code signal having an invarient frequency, an angle modulation responsive detector at a receiver responsive to said subcarrier to provide a code identifying the program transmitted, a noise responsive first timing means responsive to the output of said detector to provide a first timing signal in response to the quieting of the output of said detector for a first predetermined time period during receipt of said initial portion of said code signal, a normally closed gate, said code being applied to the input of said gate, and second timing means responsive to said timing signal and coupled to said gate to open said gate for a second predetermined time period encompassing receipt of said code.

4. The system of claim 2 further comprising:

means to angle modulate said code signal on a subcarrier, the initial portion of said code signal having an invarient frequency, an angle modulation responsive detector at a receiver responsive to said subcarrier to provide a code identifying the program transmitted, a noise responsive first timing means responsive to the output of said detector to provide a first timing signal in response to the quieting of the output of said detector for a first predetermined time period during receipt of said initial portion of said code signal, a normally closed gate, said code being applied to the input of said gate, and second timing means responsive to said timing signal and coupled to said gate to open said gate for a second predetermined time period encompassing receipt of said code.

5. The system of claim 1 further comprising:

filter means to filter out those audio program material signal frequencies corresponding to the audio frequencies of said code signal to provide a filtered program signal, switch means to couple the path for the audio program material signal through said filter means substantially only when said code signal is being provided, and means to add said code signal and said filtered program signal.

6. The system of claim 4 further comprising:

filter means to filter out those audio program material signal frequencies corresponding to the audio frequencies of said code signal to provide a filtered program signal, switch means to couple the path for the audio program material signal through said filter means substantially only when said code signal is being provided, and means to add said code signal and said filtered program signal.

7. The system of claim 1 wherein:

said means for generating said code signal generates a code signal that occupies a narrow audio band, said initial portion comprising a first frequency near the center of said narrow audio band, and said identification code portion comprising second and third frequencies bracketing said first frequency and representing the bits of a binary code.

8. The system of claim 6 wherein:

said means for generating said code signal generates a code signal that occupies a narrow audio band, said initial portion comprising a first frequency near the center of said narrow audio band, and said identification code portion comprising second and third frequencies bracketing said first frequency and representing the bits of a binary code.

9. The system of claim 1 further comprising:

receiver means responsive solely to said initial portion to provide an enabling signal in response thereto, and recording means enabled by said enabling signal and when so enabled, responsive to said identification code portion to provide a record of that identification code portion.

10. The system of claim 1 further comprising:

first timing means at a receiver responsive to said initial portion of said code signal to provide a timing signal, detector means responsive to said identification code portion to provide a code indicative of the program transmitted, a normally closed gate, said code being applied to the input of said gate, second timing means responsive to said timing signal and coupled to said gate to open said gate for a predetermined time period synchronized to encompass receipt of said code.

11. The system of claim 1 further comprising:

a recorder coupled to the output of said gate to record said code, a clock having an output adapted to be recorded on said recorder, and third timing means to apply said output of said clock to said recorder after said predetermined time period determined by said second timing means.

12. An automatic code detecting apparatus for receiving a transmitted audio program signal containing a substantially inaudible audio frequency code signal, the code signal including an initial portion and a multi-bit identification code portion, said code signal being within the frequency band width of the audio program signal and occupying a frequency band width that is at least a decade in magnitude less than the frequency band width of said audio program signal, comprising:

detecting means for detecting the transmitted audio program signal, band pass filter means coupled to the output of said signal detecting means to pass substantially only those frequencies within said frequency band of said code signal, means coupled to the output of said band pass filter and responsive to said initial portion of said code signal to provide a timing signal, detector means responsive to said identification portion of said code signal to provide a code identifying the program transmitted, normally closed gating means, said code being applied to the input of said gating means, and first timing means responsive to said timing signal and coupled to said gating means to open said gating means for a predetermined time period encompassing receipt of said code.

13. The code detecting apparatus of claim 12 wherein said initial portion of said code signal has a constant frequency and said code signal is angle modulated onto a subcarrier, and wherein:

said detector means is an angle modulation detector responsive to said subcarrier, and said first timing means is noise responsive and responsive to the output of said detector to provide said first timing signal in response to the quieting of the output of said detector for a predetermined time period during receipt of said initial portion of said code signal.

14. The apparatus of claim 12 further comprising:

a recorder coupled to the output of said gating means to record said code, a clock having an output adapted to be recorded on said recorder, clock timing means to apply said output of said clock to said recorder afteR said predetermined time period determined by said first timing means.

15. The apparatus of claim 13 further comprising:

a recorder coupled to the output of said gating means to record said code, a clock having an output adapted to be recorded on said recorder, clock timing means to apply said output of said clock to said recorder after said predetermined time period determined by said first timing means.

16. The apparatus of claim 12 further comprising:

automatic frequency control means coupled to the output of said filter means and responsive to said initial portion of said code signal to provide frequency control for said code signal, and second timing means responsive to said timing signal to freeze said automatic frequency control prior to receipt of said identification code portion of said code signal.

17. The system of claim 15 further comprising:

automatic frequency control means at the receiver responsive to said initial portion of said code signal to provide frequency control for said code signal, and means responsive to said timing signal to freeze said automatic frequency control prior to receipt of said identification code portion of said code signal.