IN-BAND DATA TRANSMISSION SYSTEM

• US 3,735,048 A
• Filed: 05/28/1971
• Issued: 05/22/1973
• Est. Priority Date: 05/28/1971
• Status: Expired due to Term

• Current Assignee: Bruce C. Eastmond, Stanley J. Tomsa
• Original Assignee: Bruce C. Eastmond, Stanley J. Tomsa
• Inventors: Tomsa, Stanley J., Eastmond, Bruce C.
• Primary Examiner(s): Blakeslee, Ralph D.
• Application Number:
  US05/148,040
• Time in Patent Office: 725 Days
• Field of Search: 179/2DP,15BM 325/26
• US Class Current: 370/528
• CPC Class Codes: H04B 7/082 selecting best antenna path

Abstract

An information transmission system for transmitting data signals simultaneously with audio signals in an audio channel includes a gate circuit at the transmitting unit for interrupting the transmitted audio at a rate controlled by the data signal, and a detector at the receiving unit for detecting the interruptions in the audio and reconstructing the data signal from the interruptions. The duration of the interruptions is selected to be short enough so as not to be readily detectable audibly. The system is suitable for use in a multiple radio-receiver system wherein signals are transmitted from spaced receivers to a central station with data signals indicating the quality of the signals received at each receiver.

Claims

1. In an information transfer system for transferring audio and data signals simultaneously within a common frequency band, with substantially no interference between the signals, a transmitting unit including in combination, audio means for providing audio signals, noise signal means for providing noise signals, summing means coupled to said audio means and said noise signal means for receiving said audio signals and said noise signals and providing sum signals of said audio signals and said noise signals, an electronic audio gate circuit coupled to said summing means and receiving the sum signals therefrom, data signal means providing variable rate data signals, said data signal means being coupled to said audio gate circuit and Cooperating therewith to cause said audio gate circuit to interrupt the sum signals at said data signal rate for intervals having a fixed time duration thereby providing data modified audio signals.

2. An information transfer system as recited in claim 1 wherein said data signal means includes interruption pulse generating means responsive to said data signals and providing interruption signals of a fixed duration at a rate varying in accordance with a predetermined characteristic of said data signals, said interruption pulse generating means being coupled to said gate circuit and applying said interruption signals thereto, said audio gate circuit being responsive to said interruption signals for interrupting the audio signals for a duration and rate determined by said interruption signals to provide said data modified audio signal.

3. An information transfer system as recited in claim 1 wherein said data signal rate is less than five interruptions per second and said time duration is less than 20 milliseconds.

4. An information transfer system as recited in claim 1 further including receiving means comprising, means for receiving said data modified audio signals, audio translating means coupled to said signal receiving means for receiving said data modified audio signals for translation thereof, interruption detection means coupled to said signal receiving means for receiving said data modified signals for detecting the rate of interruption thereof, said interruption detection means providing output signals having a characteristic varying with said interruption rate.

5. An information transfer system as recited in claim 4 wherein said interruption detection means includes, audio amplifying means coupled to receive said data modified audio signal for amplification thereof, limiting means coupled to said amplifying means receiving signals therefrom and providing a limited output signal of substantially constant amplitude, and amplitude detection means coupled to said limiting means receiving amplitude limited signals therefrom and providing output signals, said output signals having characteristics varying with the transmitted data signals.

6. An information transfer system as recited in claim 1 including receiving means comprising, means for receiving said data modified audio signal, audio reproducing means including audio amplifier means and loudspeaker means for receiving said data modified audio signals for amplification and reproduction thereof, interruption detection means comprising amplifier means for amplifying said data modified audio signals, limiter means for limiting the maximum amplitude of said audio signals to produce amplitude limited signals, amplitude detector means for detecting the amplitude of said limited signals and providing detected signals when the amplitude of said limited signals is less than said maximum amplitude, said detected signals having characteristics varying in accordance with said limited signals, and output means receiving said detected signals and providing output signals having characteristics varying with said detected signal.

7. In an information transfer system for transferring audio and data signals simultaneously within a common frequency band, with substantially no interference between the signals, a receiving unit including in combination, means for receiving a data modified audio signal, audio translating means coupled to said signal receiving means for receiving said data modified audio signal for translation thereof, interruption detection means coupled to said signal receiving means for receiving said data modified audio signals for detecting the rate of interruption thereof, said interruption detection means including limiter means for receiving the data modified audio signals and limiting the maximum amplitude thereof to provide limited signals having a first constant amplitude when no interruption is present in said data modified audio signals and having a second lower amplitude when an interruptIon is present, and a detector circuit coupled to said limiter means and receiving said limited signals, said detector circuit being responsive to the amplitude of said limited signals to provide detected signals having an amplitude varying in accordance with the rate of alternation of said limited signals between said first and second amplitudes.

8. An information transfer system as recited in claim 7 wherein said interruption detection means includes a limiter which receives the data modified audio signals and limits the maximum amplitude thereof to provide limited signals having a first constant amplitude when no interruption is present in said data modified signals and having a second lower amplitude when an interruption is present, and a detector circuit coupled to said limiter and receiving said limited signals to provide detected signals having a predetermined characteristic varying in accordance with the characteristic of said limited signals,.

9. A method of transmitting and receiving data signals simultaneously with an audio signal without causing interference between the signals, said method comprising the steps of, applying the audio signal to a transmission medium, completely interrupting the application of any signal to said transmission medium for periods of fixed duration at a rate varying in accordance with the data being transmitted, the rate of interruption being chosen not to exceed approximately five interruptions per second and the time duration of each interruption being chosen not to exceed approximately 20 milliseconds so that the audio signal is not substantially degraded by said interruptions, receiving the interrupted audio signal from said transmission medium, translating the interrupted audio signal to substantially reproduce the audio signal, detecting a lack of signal indicative of the interruptions of the audio signal, and providing an output signal that varies in response to the rate of said interruptions representative of the transmitted data signal.

10. The method recited in claim 9 wherein the step of detecting said interruptions includes the steps of, amplifying the interrupted audio signal to provide an amplified signal, limiting the maximum amplitude of the amplified signal to provide a limited signal, and detecting decreases in the amplitude of the limited signal.

11. The method recited in claim 10 further including the steps of providing a noise signal, and combining the noise signal with the audio signal prior to the interruption thereof.