Method and circuit for telephone dialing signal generation
First Claim
1. A method for generating a time varying signal that approximates a signal having a sinusoidal waveform, said method comprising the steps of:
- forming a positively sloped portion of a periodic trapezoidal waveform, wherein the strength of said signal varies with time from a minimum value to a maximum value, and wherein the duration of said positively sloped portion is substantially equal to one third of the period of said sinusoidal waveform;
forming a first constant value portion of said periodic trapezoidal waveform after said positively sloped portion, wherein the strength of said signal equals said maximum value, and wherein the duration of said first constant value portion is substantially equal to one sixth of said period;
forming a negatively sloped portion of said periodic trapezoidal waveform after said first constant value portion, wherein the strength of said signal varies with time from said maximum value to said minimum value, and wherein the duration of said negatively sloped portion is substantially equal to one third of said period; and
forming a second constant value portion of said periodic trapezoidal waveform after said negatively sloped portion, wherein the strength of said signal equals said minimum value, and wherein the duration of said second constant value portion is substantially equal to one sixth of said period.
1 Assignment
0 Petitions
Accused Products
Abstract
A method for approximating signals having sinusoidal waveforms with signals having trapezoidal waveforms, and a circuit for generating digital dual-tone multi-frequency (DTMF) dialing signals. The trapezoidal waveforms have sloped portions each equal in duration to one third of a period, and flat portions each equal in duration to one sixth of the period. DTMF dialing signals are generated by forming two such trapezoidal waveforms. The circuit forms trapezoidal waveforms by a computational technique. A periodic triangular waveform is first formed by repetitiously adding and subtracting an incremental value at a succession of time intervals. Then, the peaks of the triangular waveform are truncated to form the trapezoidal waveform.
22 Citations
29 Claims
-
1. A method for generating a time varying signal that approximates a signal having a sinusoidal waveform, said method comprising the steps of:
-
forming a positively sloped portion of a periodic trapezoidal waveform, wherein the strength of said signal varies with time from a minimum value to a maximum value, and wherein the duration of said positively sloped portion is substantially equal to one third of the period of said sinusoidal waveform; forming a first constant value portion of said periodic trapezoidal waveform after said positively sloped portion, wherein the strength of said signal equals said maximum value, and wherein the duration of said first constant value portion is substantially equal to one sixth of said period; forming a negatively sloped portion of said periodic trapezoidal waveform after said first constant value portion, wherein the strength of said signal varies with time from said maximum value to said minimum value, and wherein the duration of said negatively sloped portion is substantially equal to one third of said period; and forming a second constant value portion of said periodic trapezoidal waveform after said negatively sloped portion, wherein the strength of said signal equals said minimum value, and wherein the duration of said second constant value portion is substantially equal to one sixth of said period. - View Dependent Claims (2, 3, 4)
-
-
5. A method for generating dual-tone multi-frequency telephone dialing signals, said signals approximating two time varying signals having sinusoidal waveforms, said method comprising the steps of:
-
forming a positively sloped portion of a first periodic trapezoidal waveform having a duration substantially equal to one third of the period of a first sinusoidal waveform, wherein the strength of a first signal varies with time from a first minimum value to a first maximum value; forming a first constant value portion of said first periodic trapezoidal waveform after said positively sloped portion and having a duration substantially equal to one sixth of the period of said first sinusoidal waveform, wherein the strength of said first signal equals said first maximum value; forming a negatively sloped portion of said first periodic trapezoidal waveform after said first constant value portion and having a duration substantially equal to one third of the period of said first sinusoidal waveform, wherein the strength of said first signal varies with time from said first maximum value to said first minimum value; forming a second constant value portion of said first periodic trapezoidal waveform after said negatively sloped portion and having a duration substantially equal to one sixth of the period of said first sinusoidal waveform, wherein the strength of said first signal equals said first minimum value; forming a positively sloped portion of a second periodic trapezoidal waveform having a duration substantially equal to one third of the period of a second sinusoidal waveform, wherein the strength of a second signal varies with time from a second minimum value to a second maximum value; forming a first constant value portion of said second periodic trapezoidal waveform after said positively sloped portion and having a duration substantially equal to one sixth of the period of said second sinusoidal waveform, wherein the strength of said second signal equals said second maximum value; forming a negatively sloped portion of said second periodic trapezoidal waveform after said first constant value portion and having a duration substantially equal to one third of the period of said second sinusoidal waveform, wherein the strength of said second signal varies with time from said second maximum value to said second minimum value; forming a second constant value portion of said second periodic trapezoidal waveform after said negatively sloped portion and having a duration substantially equal to one sixth of the period of said second sinusoidal waveform, wherein the strength of said second signal equals said second minimum value; and combining said first and second periodic trapezoidal waveforms to generate a dual-tone multi-frequency telephone dialing signal. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13)
-
-
14. A method for generating a time varying signal that approximates a signal having a sinusoidal waveform, said method comprising the steps of:
-
forming a periodic triangular waveform having a period substantially equal to that of said sinusoidal waveform, said periodic triangular waveform having a positively sloped portion extending from a minimum value to a maximum value, and a negatively sloped portion extending from said maximum value to said minimum value, wherein said positively and negatively sloped portions have slopes of equal magnitude; and forming said signal by truncating said triangular waveform to create a trapezoidal waveform, said trapezoidal waveform having an upper constant value portion equal in value to an upper extreme value and extending for a duration substantially equal to one sixth of said period, and also having a lower constant value portion equal in value to a lower extreme value and extending for a duration substantially equal to one sixth of said period. - View Dependent Claims (15, 16, 17, 18)
-
-
19. A digital circuit for generating a time varying signal that approximates a signal having a sinusoidal waveform, said circuit comprising:
-
means for forming a positively sloped portion of a periodic trapezoidal waveform, wherein the strength of said signal varies with time from a minimum value to a maximum value, and wherein the duration of said positively sloped portion is substantially equal to one third of the period of said sinusoidal waveform; means for forming a first constant value portion of said periodic trapezoidal waveform after said positively sloped portion, wherein the strength of said signal equals said maximum value, and wherein the duration of said first constant value portion is substantially equal to one sixth of said period; means for forming a negatively sloped portion of said periodic trapezoidal waveform after said first constant value portion, wherein the strength of said signal varies with time from said maximum value to said minimum value, and wherein the duration of said negatively sloped portion is substantially equal to one third of said period; and means for forming a second constant value portion of said periodic trapezoidal waveform after said negatively sloped portion, wherein the strength of said signal equals said minimum value, and wherein the duration of said second constant value portion is substantially equal to one sixth of said period. - View Dependent Claims (20, 21)
-
-
22. A digital circuit for generating a time varying signal that approximates a signal having a sinusoidal waveform, said circuit comprising:
-
means for periodically adding and subtracting an incremental value at a succession of time intervals to generate a periodic triangular waveform, said means including arithmetic means for performing arithmetic operations, wherein said arithmetic means is capable of generating output signals having values not less than a minimum value and not greater than a maximum value, a memory register coupled to said arithmetic means for temporarily storing the value of said triangular waveform, saturation detection means coupled to said arithmetic means for indicating saturation when said arithmetic means reaches either its maximum or minimum value; and control means for periodically directing said arithmetic means to increment the value of said trangular waveform by an incremental value, and for changing the sign of said incremental value when accumulator saturation is detected, wherein the magnitude of said incremental value is chosen such that the period of said signal is equal to the period of said sinusoidal waveform; and means for truncating said triangular waveform to form a trapezoidal waveform, wherein said time varying signal equals the time varying value of said trapezoidal waveform. - View Dependent Claims (23, 24, 25)
-
-
26. A digital circuit for generating a time varying signal having a trapezoidal waveform approximating a signal having a sinusoidal waveform, said circuit comprising:
-
arithmetic means for performing arithmetic operations, wherein said arithmetic means is capable of generating digital values not less than a minimum value and not greater than a maximum value; a memory register coupled to said arithmetic means for temporarily storing the value of a triangular waveform; saturation detection means coupled to said arithmetic means for indicating saturation when said arithmetic means reaches either its maximum or minimum value; and control means for periodically directing said arithmetic means to increment the value of said triangular waveform by an incremental value and to multiply the value of said triangular waveform by a multiplier to yield said signal, and for changing the sign of said incremental value when accumulator saturation occurs during incrementation, wherein the magnitude of said incremental value is chosen such that the period of said signal is equal to the period of said sinusoidal waveform. - View Dependent Claims (27, 28, 29)
-
Specification