Telephone signal classification and phone message delivery method and system

• US 5,311,575 A
• Filed: 06/22/1993
• Issued: 05/10/1994
• Est. Priority Date: 08/30/1991
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Oh, Sang G.
• Primary Examiner(s): Dwyer, James L.
• Assistant Examiner(s): Tsang, Fan
• Application Number:
  US08/081,481
• Time in Patent Office: 322 Days
• Field of Search: 379/372, 379/377, 379/381, 379/386, 379/351, 379/80, 379/88, 381/41, 381/46, 381/47
• US Class Current: 379/88.01
• CPC Class Codes: G10L 25/78 Detection of presence or absence of voice signals switching of direction of transmission by voice frequency in two-way loud-speaking telephone systems H04M9/10
• CPC Class Codes: H04M 3/533 Voice mail systems
• CPC Class Codes: H04Q 1/30 Signalling arrangements; Manipulation of signalling currents multiplex systems providing for calling or supervisory signals H04J1/14, H04J3/12

Abstract

A method of processing a signal having characteristics and received from a telephone line is presented. The method includes defining a frame by measuring a plurality of samples from the signal over a predetermined period. Additionally, linear prediction coding coefficients of a selected group from the plurality of samples are determined. Further, the variance of the linear prediction coding coefficients are determined and the variances compared to a reference variance. A heuristic rule is applied to a selected characteristic of the signal to determine if the signal comprises a voice signal.

Claims

1. A method of processing a received signal having characteristics and received from a telephone line to determine if a true voice signal, comprising:

defining a frame by measuring a plurality of samples from said received signal over a predetermined period;

determining the linear prediction coding coefficients of a selected group of the plurality of samples;

determining the variance of the linear prediction coding coefficients;

comparing the variance to a reference variance; and

applying a heuristic rule based on a ring signal, a click signal, a reorder signal, or a busy signal on a telephone line to a selected characteristic of said received signal to determine if said received signal comprises a voice signal and not a ring signal, a click signal, a reorder signal or a busy signal.

2. The method of claim 1 wherein said applying a heuristic rule step includes a step of determining the root mean square of the plurality of samples over the predetermined period.

3. The method of claim 1 wherein said step of measuring over a predetermined period comprises measuring over a period of 64 milliseconds.

4. The method of claim 3 wherein said step of measuring a plurality of samples comprises measuring 512 samples over the period of 64 milliseconds.

5. The method of claim 1 wherein said step of measuring a plurality of samples comprises measuring 512 samples.

6. The method of claim 5 wherein said step of determining the linear prediction coding coefficients of a selected group from the plurality of samples comprises determining the linear prediction coding coefficients of every fourth sample of the plurality of samples.

7. The method of claim 5 wherein said step of determining the linear prediction coding coefficients of a selected group from the plurality of samples comprises determining the linear prediction coding coefficients of every sample of the plurality of samples.

8. The method of claim 1 wherein said step of determining the linear prediction coding coefficients of a selected group from the plurality of samples comprises determining the linear prediction coding coefficients of 128 of the 512 measured samples.

9. The method of claim 1 wherein said reference variance comprises a first reference variance, and further comprising the step of comparing the variance to a second reference variance.

10. The method of claim 1 wherein said reference variance comprises a first reference variance, and further comprising the steps of:

comparing the variance to a second reference variance; and

comparing the variance to a third reference variance.

11. The method of claim 10 wherein each of said comparisons of the variance with a reference variance comprises comparing the variance with a first, second or third reference representing a ring signal reference.

12. The method of claim 1 wherein said step of applying a heuristic rule to a selected characteristic of said received signal comprises evaluating a duration of multiple frames under the heuristic rule that the duration of a ring signal is at least 0.9 seconds but not longer than 2.5 seconds.

13. The method of claim 1 wherein said step of applying a heuristic rule to a selected characteristic of said received signal comprises evaluating a frame under the heuristic rule that the root mean square of a ring signal remains relatively constant during the period of the frame.

14. The method of claim 1 wherein said step of applying a heuristic rule to a selected characteristic of said received signal comprises evaluating a duration of multiple frames under the heuristic rule that the duration of a click signal is at most 0.25 seconds.

15. The method of claim 1 wherein said step of applying a heuristic rule to a selected characteristic of said received signal comprises evaluating a frame under the heuristic rule that the root mean square of a voice signal varies significantly over a period of the frame.

16. The method of claim 1 wherein said step of applying a heuristic rule to a selected characteristic comprises a step of measuring the zero crossing of said received signal during the predetermined period.

17. The method of claim 1 wherein said step of applying a heuristic rule to a selected characteristic of said received signal comprises evaluating a duration of multiple frames under the heuristic rule that the on/off interval of a busy signal is approximately 500 milliseconds.

18. The method of claim 1 wherein said step of applying a heuristic rule to a selected characteristic of said received signal comprises evaluating a duration of multiple frames under the heuristic rule that the on/off interval of a reorder signal is approximately 250 milliseconds.

19. A method of processing a received signal having characteristics and received from a telephone line to determine if a true voice signal, comprising:

defining a frame by measuring a plurality of samples from said received signal over a predetermined period;

determining the root means square of the plurality of samples over the predetermined period;

determining the linear prediction coding coefficients of a selected group of the plurality of samples;

determining the variance of the linear prediction coding coefficients;

comparing the variance to a first reference variance;

comparing the variance to a second reference variance;

comparing the variance to a third reference variance; and

applying a heuristic rule based on a ring signal, a reorder signal, a click signal or a busy signal to a selected characteristic of said received signal to determine if the signal is a voice signal and not a ring signal, a reorder signal, a click signal or a busy signal.

20. The method of claim 19 wherein said step of measuring a plurality of samples comprises measuring 512 samples over the period of 64 milliseconds.

21. The method of claim 19 wherein said step of determining the linear prediction coding coefficients of a selected group from the plurality of samples comprises determining the linear prediction coding coefficients of every fourth sample of the plurality of samples.

22. The method of claim 19 wherein each of said comparisons of the variance with a reference variance comprises comparing the variance with a first, second or third reference representing a ring signal reference.

23. The method of claim 19 wherein said step of applying a heuristic rule to a selected characteristic of said received signal comprises evaluating a duration of multiple frames under the heuristic rule that the duration of a ring signal is at least 0.9 seconds but not longer than 2.5 seconds.

24. The method of claim 19 wherein said step of applying a heuristic rule to a selected characteristic of said received signal comprises evaluating a frame under the heuristic rule that the root mean square of a ring signal remains relatively constant during a period of the frame.

25. The method of claim 19 wherein said step of applying a heuristic rule to a selected characteristic of said received signal comprises evaluating a duration of multiple frames under the heuristic rule that the duration of a click signal is at most 0.25 seconds.

26. The method of claim 19 wherein said step of applying a heuristic rule to a selected characteristic of said received signal comprises evaluating a frame under the heuristic rule that the root mean square of a voice signal varies significantly over a period of the frame.

27. The method of claim 19 wherein said step of applying a heuristic rule to a selected characteristic of said received signal comprises a step of measuring the zero crossing of said received signal during the predetermined period.

28. The method of claim 19 wherein said step of applying a heuristic rule to a selected characteristic of the signal comprises evaluating a duration of multiple frames under the heuristic rule that the on/off interval of a busy signal is approximately 500 milliseconds.

29. The method of claim 19 wherein said step of applying a heuristic rule to a selected characteristic of the signal comprises evaluating a duration of multiple frames under the heuristic rule that the on/off interval of a reorder signal is approximately 250 milliseconds.

30. A method of processing a received signal having characteristics and received from a telephone line to determine if a true voice signal, comprising:

defining a frame by measuring a plurality of samples from said received signal over a predetermined period;

determining the root mean square of the plurality of samples over the predetermined period;

measuring the zero crossing of the signal during the predetermined period;

determining the linear prediction coding coefficients of a selected group of the plurality of samples;

determining the variance of the linear prediction coding coefficients;

comparing the variance to a reference variance; and

applying heuristic rules based on a ring signal, a reorder signal, a click signal or a busy signal to selected characteristics of said received signal to determine if said received signal comprises a voice signal and not a ring signal, a reorder signal, a click signal, or a busy signal.

31. The method of claim 30 wherein said reference variance comprises a first reference variance, and further comprising the steps of:

comparing the variance to a second reference variance; and

comparing the variance to a third reference variance.

32. The method of claim 30 wherein said step of applying heuristic rules to selected characteristics of said received signal comprises:

evaluating a duration of multiple frames under the heuristic rule that the duration of a ring signal is at least 0.9 seconds but not longer than 2.5 seconds; and

evaluating a frame under the heuristic rule that the root mean square of a ring signal remains relatively constant during the period of the frame.

33. The method of claim 30 wherein said step of applying heuristic rules to selected characteristics of said received signal comprises evaluating a duration of multiple frames under the heuristic rule that the duration of a click signal is at most 0.25 seconds.

34. The method of claim 30 wherein said step of applying heuristic rules to selected characteristics of said received signal comprises evaluating a frame under the heuristic rule that the root mean square of a voice signal varies significantly over the period of the frame.

35. The method of claim 30 wherein said step of applying heuristic rules to selected characteristics of said received signal comprises:

evaluating a duration of multiple frames under the heuristic rule that the on/off interval of a busy signal is approximately 500 milliseconds; and

evaluating a duration of multiple frames under the heuristic rule that the on/off interval of a reorder signal is approximately 250 milliseconds.

36. An automated method of transferring a voice telephone message to an intended recipient in a telephone message delivery system comprising the steps of:

a) receiving a telephone voice message;

b) storing the received message in a storage device;

c) calling an intended recipient;

d) processing a received signal from said recipient having characteristics and received from a telephone line to determine if a true voice signal, comprising the steps of;

e) defining a frame by measuring a plurality of samples from said received signal over a predetermined period;

f) determining the linear prediction coding coefficients of a selected group of the plurality of samples;

g) determining the variance of the linear prediction coding coefficients;

h) comparing the variance to a reference variance;

i) applying a heuristic rule based on a ring signal, a reorder signal, a click signal or a busy signal on a telephone line to a selected characteristic of said received signal to determine if said received signal comprises a voice signal and not a ring signal, a reorder signal, a click signal or a busy signal; and

j) delivering said message if said voice signal is determined.

37. The method of claim 36, wherein an storing step includes storing said indication of the recipient.

38. The method of claim 36, including the step of repeating the steps c through i to identify a voice signal when said received signal from said recipient is not a voice signal.

39. The method of claim 38, wherein said step of applying a heuristic rule to selected characteristics comprises evaluating a duration of multiple frames under the heuristic rule that the duration of a signal if at least 0.9 seconds but not longer than 2.5 seconds.

40. The method of claim 39, wherein said step of applying a heuristic rule to selected characteristics further comprises evaluating a frame under a heuristic rule that the root means square of a ring signal remains relatively constant during a period of the frame.

41. The method of claim 36, wherein said step of applying a heuristic rule to selected characteristics of said received signal comprises evaluating a duration of multiple frames under heuristic rule that the duration of a click signal is at most 0.25 seconds.

42. The method of claim 36, wherein said step of applying a heuristic rule to selected characteristics of said received signal comprises evaluating a frame under the heuristic rule that the root mean square of a voice signal varies significantly over a period of the frame.

43. The method of claim 36, wherein said step of applying a heuristic rule to selected characteristics of said received signal comprises;

evaluating a duration of multiple frames under the heuristic rule that the on/off interval of a busy signal is approximately 500 milliseconds; and

evaluating a duration of multiple frames under the heuristic rule that the on/off interval of a reorder signal is approximately 250 milliseconds.