CN1147740A - Chip for detecting telephone signals with digital signal processor and performing digital communication - Google Patents
Chip for detecting telephone signals with digital signal processor and performing digital communication Download PDFInfo
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- CN1147740A CN1147740A CN 96111377 CN96111377A CN1147740A CN 1147740 A CN1147740 A CN 1147740A CN 96111377 CN96111377 CN 96111377 CN 96111377 A CN96111377 A CN 96111377A CN 1147740 A CN1147740 A CN 1147740A
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Abstract
The chip may be widely used for detecting various telephone network signals in telephones and facsimile printers as well as for point-to-point data communication. The hardware structure of the chip includes anti-jamming filter, A/D contertor, digital signal processor, data input memory, signal output encoder, ROM, RAM and other units. Without needing expansion, the chip can expand the sorts of signals to be identified.
Description
The chip that the present invention detects various telephone signals and carries out data communication for a kind of use digital signal processor (DSP).
Press, the device that carries out the telephone signal detection at present in the telephone set all is to realize by wave filter technology, the defective of this kind technology is all need design a special filter for each frequency, so its design and cost of manufacture on hardware device is quite high, even utilize digital signal processor or utilize software simulation, its program is also rather complicated, is difficult to expand, and the demand that also can't meet in the ordinary course of things, data communication.
The objective of the invention is to solve the defective that the device that carries out the telephone signal detection in the conventional telephone set is difficult to expand and can't satisfy data communication technically, the assembly type chip that is provided is provided, need not carry out under the situation of any expansion, just can expand the kind of identification signal easily.
Fig. 1 is a hardware structure schematic diagram of the present invention;
Fig. 2 is the stopband/pass band damping characteristic schematic diagram of interference resistant filter of the present invention;
Fig. 3 is the logic block schematic diagram of digital signal processor of the present invention (DSP);
Fig. 4 is the hardware structure schematic diagram of one embodiment of the invention;
Fig. 5 is the logic block schematic diagram of the digital signal processor (DSP) of one embodiment of the invention.
Hardware structure of the present invention, consult shown in Figure 1, mainly be by interference resistant wave filter 1, analog-digital converter (A/D) 2, digital signal processor (DSP) 3, data input store 4, seven parts such as signal output coder 5 and read-only storage (ROM) 6 and random access memory (RAM) 7 form, wherein this interference resistant wave filter 1 is connected other data input store 4 via analog-digital converter (A/D) 2 with digital signal processor (DSP) 3, signal output coder 5,7 of read-only storage (ROM) 6 and random access memory (RAM) are connected with this digital signal processor (DSP) 3 respectively.
Interference resistant filter 1 of the present invention mainly before carrying out analog-to-digital conversion, will be lower than the frequency filtering of half sampling frequency.Because, the typical bands at phone networking is 300-700Hz, and the generally the highest 300Hz that is no more than of the signal on the phone networking, so, the sampling frequency that this wafer uses is decided to be 6400Hz, this promptly requires the above signal of interference resistant filter elimination 3200Hz, the characteristic of interference resistant filter as shown in Figure 2, its stopband should be than pass band damping at least more than the 40DB.If the analog to digital converter 2 that is adopted has the function of interference resistant, then this partial circuit can omit.
Analog to digital converter of the present invention (A/D) the 2nd is a digital signal with analog signal conversion, and this is to carry out signal processing because of the core of chip of the present invention system uses digital method.So, must be the digital signal that digital signal processor can be discerned with analog signal conversion by analog to digital converter 2.In addition, because the signal amplitude on the telephone wire has very big dynamic range, often more than 40db, the conversion range of its analog to digital converter also should be greater than 40db, so the quantification (Quantitative) after its conversion should be worked energetically 14bit than coefficient.
Digital signal processor of the present invention (DSP) 3 is the core of this chip, meaning is that whole signal processing and other necessary digital processings all carried out via this digital signal processor 3, when the running beginning, earlier the instruction code in the read-only memory 6 is written in the high-speed random access memory 7, and then carries out necessary digital processing by digital signal processor 3.
Data of the present invention input holder 4 be with input data storing in holder, determining the kind of measured signal, 5 of signal output coders be will signal through the output of coding back, read-only memory 6 is employing 32K
*16 read-only memory, random access memory 7 then are to adopt 32K
*16 high-speed random access memory.
Consult shown in Figure 3, Fig. 3 is the logic calcspar of this digital signal processor (DSP) 3, at first, when data input cell 8 coefficient word signal processors (DSP) 3 are accepted from the digital signal of analog to digital converter (A/D) 2, according to the size of data in the nearest 10ms, maximizing is as normalization (Normalize) constant, and after data being done the amplification of correspondence, be sent to discrete Fourier transform (DFT) unit 9.
The main feature that this discrete Fourier transform (DFT) unit 9 is different from other telephone signal detector is, can be by the discrete Fourier transform by signal calculated, to understand the distribution situation of signal on whole frequency domain.Because this unary system is to the analysis of whole frequency band, so, can expand easily, and not need extra cost.The computational methods of this discrete Fourier transform (DFT) unit 9 are to use 256 point quick Fourier conversion (FFT).Because chip of the present invention can adopt the sampling rate of 6400Hz, therefore, calculating resulting frequency domain precision via 256 point quick Fourier conversion (FFT) is 6400/256=25Hz.In addition, when calculating discrete Fourier transform (DFT), if counting of calculating is many more, the precision (frequency resolution) of the frequency domain parameter that then obtains is higher, but amount of calculation also is the index raising simultaneously, and computing time is also just long, and the frequency distribution of its gained is long mean value, time precision is low more, and the time precision of the signal of telephone wire often must be more than 10ms.So, if the present invention complies with the computational speed of the digital signal processor that is adopted, the time precision of chip is set in 10ms, the calculating of discrete Fourier transform (DFT) counted be limited in 256 points, then under the sampling rate of 6400Hz, its frequency accuracy (frequency resolution) is 6400/256=25Hz.
Wait through aforementioned discrete Fourier transform (DFT) calculating after, can obtain complete frequency distribution situation, via detecting unit 10, the energy size of the frequency that observation post need detect, can determine whether this frequency exists, be provided with a threshold value (Threshold) in this unit, if the energy of frequency is higher than this threshold value, can think that then this frequency exists, otherwise, think that then this frequency does not exist, this threshold value takes to be a key factor that detects really as, and this threshold value must be determined via testing.In addition and since the signal on the phone networking often be double-tone frequently, so when detecting, need to consider two frequencies that all exist as two frequencies, then this signal exists, and does not exist if any a frequency, then this signal does not exist.
This detecting unit 10 and during with a batch total unit 11 be connected, carrying out time counting at signal, institute of time response system some (or a plurality of) frequency that shows of telephone signal exists and the time span of disappearance.According to aforementioned calculate via discrete Fourier transform (DFT) after, be distributed in the signal output on the frequency domain, if (or a plurality of) frequency exists, then this signal exists in 10ms, increase by 1 unit with the existing timing unit of signal this moment, otherwise, the non-existent timing unit of signal is increased by 1 unit.If chip of the present invention is to adopt every 10ms according to discrete Fourier transform (DFT) mode to calculate once, then the time precision that whether exists of signal is 10ms.
These timing units 11 are connected with matching unit 12 respectively again, mate with signal and the standard signal model that will be transmitted.Signals all on the telephone network all need meet specific national standard, so carry out the output of time counting by 11 pairs of signals of aforementioned timing unit, the distribution situation of resultant signal on time-domain, can mate with the national standard model through this this matching unit 12, result system as coupling drops within the allowed band, think that then a certain telephone signal is detected, otherwise, this signal then be provided with.
Then, these matching units 12 are connected with comprehensive unit 13 again, make the output of comprehensive unit 13 comprehensive each road signal.So, wafer of the present invention can not only detect the signal of existence, and can be according to comprehensive each road signal judgment result, detect these signals and when finish, this comprehensive unit 13 is also exported the code (comprising end code) of detected coherent signal, and these codes can be defined voluntarily by the user, any one road signal is detected or finishes, the capital makes this comprehensive unit 13 output correlative codes, if this signal ended then can cause this unit 13 end of output codes.
This comprehensive unit 13 also is connected with signal output coder 5, by this signal output coder 5 signal that is detected is exported.
Data input cell 8 of the present invention again is connected with a zero-crossing rate computing unit 14, in addition with the zero-crossing rate of signal calculated.The characteristics of a sinusoidal signal, tie up to the interior zero passage of one-period twice, by calculating the zero-crossing rate N of a sinusoidal signal, just can obtain its frequency F=N/2 easily, this kind computational methods are used in the data communication, and shift frequency is sent signal (frequency-shift keying is called for short FSK) data and is made up of the sinusoidal signal of two frequencies, low frequency representative " 1 ", high frequency representative " 0 ".But first constantly, only may have the sinusoidal signal of a frequency, by simply by calculating zero-crossing rate, can be separately with two frequency zones, thus reach the purpose of differentiation " 0 " and " 1 ".
This zero-crossing rate computing unit 14 is connected with time counting unit 15, because the characteristics of fsk data are that the time that each sinusoidal signal exists is the integral multiple of certain minimum value.If the fsk signal of chip detection 1200dps of the present invention, the minimum time 1/1200=833us that exists of each signal then, again by the result of zero-crossing rate respectively to two frequency computation part, then can obtain their distribution situations on time-domain, if time precision of the present invention is the time interval 1/6400=156us of sample rate, then each band frequency will be made up of a string continuous " 0 " or " 1 ", and " 0 " that each section is continuous or the number of " 1 " have 833/156＞=5 at least.
At last, this time counting unit 15 is connected with a logic determines part 16 again, when making the present invention detect the fsk signal of 1200dbs, according to 1200Hz presentation logic " 1 ", 2400Hz presentation logic " 0 " by calculating two distributions of frequency on time-domain, converts thereof into logical zero and logical one, and initial from fsk signal, every interval 1/1200=833us extracts the logical value of a logical value as this section.Press, the present invention is in order to the form of 1200bpsFSK signal system employing a start bit, 8 data bit and a position of rest of communication, the standard of symbol CCITT.But, the form that the user also can own definition of data.
Now careful just the present invention one of is applied in the telephone set embodiment, consults shown in the Figure 4 and 5, is described in detail as follows:
Be provided with the analog to digital converter 102 of tool interference resistant function among this embodiment, this modulus adopts the oval low pass filter in 8 rank according to being provided with the interference resistant filter in the transducer 102, and its stopband is than the 40db at least that decays usually.
Digital signal processor among this embodiment (DSP) 103, its clock frequency is 40MHz, all signal processing and other necessary processing are all finished via this processor 103, data input store 104 stores the input data, in the kind of determining measured signal, signal output coder 105 is with behind the signal process coding, and detected signal is exported, and its read-only memory (ROM) 106 adopts 32K
*16 read-only memory, 107 of its random-access memory (ram)s adopt 32K
*16 high-speed random access memory.During the running beginning, earlier the instruction code in the read-only memory (ROM) 106 is written in the high-speed random access memory (RAM) 107, and then, carries out necessary digital processing by this digital signal processor (DSP) 103.
The data input cell 108 of digital signal processor among this embodiment (DSP) 103 is after accepting the digital signal that transmits from analog to digital converter, size according to data in the nearest 10ms, find out its maximum, as normaliztion constant, and data are done corresponding amplification, be sent to discrete Fourier transform (DFT) unit 109.
This discrete Fourier transform (DFT) unit 109 adopts the computational methods of fast Fourier transform (FFT).Because the computing genealogy of law of fast Fourier transform is carried out at plural number, and actual signal is real signal, and promptly its imaginary part is 0.So, can be by calculating 128 point quick Fourier conversion, obtain the value of 256 discrete Fourier transform then, so, can save the time about half approximately, simultaneously, save the memory space of half, and 256 real input signal formed one group of 128 complex signal, and its real part is the real signal of even number point, its imaginary part is the real signal of odd point:
That is: (U) i=X (2i)=jX (2i+1) i=0,1 ..., 127
The discrete Fourier transform of calculating U (i) can obtain Ur (k), Ui (k), and k=0,1 ..., 127
Calculate U (k)=1/2 (Ur (k)+Ur (128-k))+1/2j (Ui (K)-Ui (128-k))
W(k)＝1/2〔Ui(k)+Ui(128-k)〕-1/2j〔Ur(k)-Ur(128-k)〕-2πj/(2N)K
X(k)＝V(k)+W(k).e?????K＝0，1，…，127
X (k) is the discrete Fourier transform value of input real signal x (t), because X (k) is a symmetry, so, in fact only need front or back promptly enough at 128.
After present embodiment calculates discrete Fourier transform, can obtain complete frequency distribution situation, via detecting unit 110, the happy frequency of observation post is 350Hz+440Hz, 400Hz, 450Hz, 900Hz, 1400Hz, 1800Hz, 2130Hz+2750Hz, 440Hz+480Hz, 480Hz+620Hz, calculate 350 respectively, 400,440,450,480,620,900,1400,1800,2130, the energy of 2750Hz, it is compared with threshold value separately, if it is bigger, represent that then this frequency exists, if it is less, represent that then this frequency does not exist, if 350Hz and 440Hz, 440 and 480Hz, 480Hz and 620Hz, 2130Hz and 2750Hz exist simultaneously, then represent 350Hz+440Hz, 440Hz+480Hz, 480Hz+620Hz, four pairs of signals such as 2130Hz+2750Hz exist respectively, otherwise, then do not exist, the threshold value of each frequency needs to determine via experiment.
Timing unit 11 is to carry out time counting at signal among this embodiment, a unit representation 10ms, and signal exists and represents that with ON signal does not exist with OFF and represents.If there be (ON) in signal, represent that then signal exists in this 10ms, the calculated value of ON is increased by 1 unit, i.e. 10ms, otherwise representing does not have this signal in this 10ms increases by 1 unit, i.e. 10ms with the calculated value of OFF.The one group of representation signal that so, promptly forms ON-OFF has or does not have each numerical value how long.
These timing units 111 are connected with matching unit 112 respectively again, mate with signal and the standard signal model that will be transmitted, and press, and the signal that can detect among this embodiment has:
The national standard signal of Britain
| Musical alphabet | Frequency (Hz) | Waveform definition |
| Begin indication (dialing tone) | ????350+440 | Continuously |
| Special begin the indication (interruption dialing tone) | ????350+440 | 1) the continuous 350Hz pulse of 440Hz 750ms on; |
| 750ms off 2) two of above-mentioned speed pulse kinds of sounds | ||
| Wait-for-response indication (ring back tone) | 1) 400 or 450 2) 400+450 | 0.4s on 0.2s off 0.4s on 2s off 0.35s on 0.22s off is at any point beginning in:0.4s on 0.2s off 0.4s on 2s off |
| The number of accounting for indication (busy tone) | ????400 | ????0.375s?on ????0.375s?off |
| The path takies indicating equipment and takies sound | ????400 | ????0.4s?on ????0.35s?off ????0.225s?on ????0.525s?off |
| Connect not permission indication (can not obtain number) | ????400 | Continuously |
| Distinctive signal sound (SIT) | ????950 ????1400 ????1800 | With given order, each frequency send 370+/-70ms has the mute periods of growing to 30ms between two adjacent signals |
| Phone is reminded sound | ??2130+2750 | ????88-110ms |
The national standard signal of the U.S.
| Musical alphabet | Frequency (Hz) | Waveform definition |
| Dialing tone | ????350+440 | Stable state |
| Pull literary composition and wait for the indication sound | ????350+440 | 10 pulse trains (0.1s on, 0.1s off) are stable state then |
| Calling dial sound/affirmation sound again | ????350+440 | 3 pulse trains (0.1s on, 0.1s off) are stable state then |
| Line be busy | ????480+620 | 0.5s on, 0.5s off. repeats |
| Ordering again | ????480+620 | 0.25s on, 0.25s off. repeats |
| Ring-back | ????440+480 | 2s on, 4s off. repeats |
| Phone is reminded sound | ????2130+2750 | ????????????75-85ms |
At first, relatively whether measured signal is consistent with the frequency of master pattern, if inconsistent, then be judged to be the signal of non-this class standard, compare with other model, if it is consistent, then relatively the ON-OFF characteristic value of this signal whether with conformance to standard, if consistent, then be judged to be such signal, otherwise, compare with other model.
These matching units 112 are connected with comprehensive unit 113 again, make the output of comprehensive unit 113 comprehensive each road signal.So, present embodiment can not only detect the signal of existence, and can be according to comprehensive each road signal judgment result, when detect these signals finishes, this comprehensive unit 113 is also exported the code (comprising end code) of detected coherent signal, and these codes can be defined voluntarily by the user, and any one road signal is detected or finishes, the capital makes this comprehensive unit 113 correlative code immediately, and its code is:
The national standard signal code of Britain
| Sound number | Musical alphabet |
| ????01. | Begin indication (dialing tone) |
| ????02. | Special begin the indication (interruption dialing tone) |
| ????03. | Wait acknowledge indication (ring back tone) |
| ????05. | The number of accounting for indication (busy tone) |
| ????06. | Account for path indication (equipment engaged tone) |
| ????07. | Connect not permission indication (can not obtain number) |
| ????08. | Special Information Tone (SIT) |
| ????17. | Phone is reminded sound |
The national standard signal code of the U.S.
| Sound number | Musical alphabet |
| ????10. | Dialing tone |
| ????11. | Pull literary composition and wait for the indication sound |
| ????12. | Calling dial sound/affirmation sound again |
| ????13. | Line be busy |
| ????14. | Ordering again |
| ????15. | Ring-back |
| ????16. | Phone is reminded sound |
The data input cell 108 of present embodiment again, be connected with a zero-crossing rate computing unit 114 in addition, zero-crossing rate with signal calculated, press, the characteristics of a sinusoidal signal, tie up to the interior zero passage of one-period twice, by calculating the zero-crossing rate N of a sinusoidal signal, just can obtain its frequency F=N/2 easily, this kind computational methods are used in the data communication, and shift frequency is sent signal (frequency-shift keying is called for short FSK) data and is made up of the sinusoidal signal of two frequencies, 1200Hz represents " 1 ", and 2400Hz represents " 0 ".But each is constantly, only may have the sinusoidal signal of a frequency, by calculating zero-crossing rate simply, can be separately with two frequency zones, thus reach the purpose of differentiation " 0 " and " 1 ".
This zero-crossing rate computing unit 114 is connected with time counting unit 115, because, the characteristics of fsk data are that the time that each sinusoidal signal exists is the integral multiple of certain minimum value, if the fsk signal of the chip detection 1200dps of present embodiment, then the minimum time of each signal existence is 1/1200=833us, again by the result of zero-crossing rate respectively to two frequency countings, then can obtain their distribution situations on time-domain, if time precision of the present invention is the time interval 1/6400=156us of sample rate, then each band frequency will be made up of a string continuous " 0 " or " 1 ", and each section number of it " 0 " or " 1 " continuously has 833/156＞=5 at least.
At last, when logic judgment unit 116 detects the fsk signal of 1200dbs in this example, according to 1200Hz presentation logic " 1 ", 2400Hz presentation logic " 0 ", by calculating two distributions of frequency on time-domain, convert thereof into logical zero and logical one, and initial from fsk signal, every interval 1/1200=833us extracts the logical value of a logical value as this section.Press, the present invention adopts the form of a start bit, 8 data bit and a position of rest in order to the 1200bpsFSK signal of communication, meets the standard of CCITT, but, the form that the user also can own definition of data.
In addition, the above only is one of the present invention preferred embodiment, is familiar with the personage of this skill generally, and the various variations that utilize spirit of the present invention to make must be contained within the present invention.
Claims (15)
1. chip that uses digital signal processor to detect various telephone signals and carry out data communication is characterized in that this chip comprises:
One analog to digital converter is the digital signal that this digital signal processor can be discerned with analog signal conversion;
One digital signal processor is connected with analog to digital converter, handles at whole signals and necessary numeral;
One data input holder links to each other with digital signal processor, will import data storing in this holder, to determine the kind of measured signal;
One signal output coder links to each other with digital signal processor, and signal is exported through the coding back;
One random access memory links to each other with digital signal processor, adopts high-speed random access memory.
2. use digital signal processor as claimed in claim 1 detects various telephone signals and carries out the chip of data communication, it is characterized in that, the sampling frequency that this chip uses can be set at 6400Hz, promptly require the above signal of interference resistant filter filter elimination 3200Hz, its stopband is than decaying at least more than the 40DB usually.
3. use digital signal processor as claimed in claim 1 detects various telephone signals and carries out the chip of data communication, it is characterized in that the analog to digital converter that this sheet adopts has the function of interference resistant.
4. use digital signal processor as claimed in claim 1 detects various telephone signals and carries out the chip of data communication, it is characterized in that, comprises:
One interference resistant filter is connected with digital signal processor via analog to digital converter, before carrying out analog-to-digital conversion, will be lower than the frequency filtering of half sampling frequency.
5. use digital signal processor as claimed in claim 1 detects various telephone signals and carries out the chip of data communication, it is characterized in that the conversion range of this analog to digital converter is greater than 40db.
6. use digital signal processor as claimed in claim 1 detects various telephone signals and carries out the chip of data communication, it is characterized in that this digital signal processor also comprises:
One number input units, when tying up to acceptance from the digital signal of analog to digital converter output, according to the size of data in the nearest 10ms, maximizing as normaliztion constant, and is done corresponding amplification with data;
One discrete Fourier transform unit receives the signal by data input cell output, by the discrete Fourier transform by signal calculated, understands the distribution situation of signal on whole frequency domain;
One detecting unit, in order to detect the complete frequency distribution situation of gained after this direct computation of DFT transformation calculations, the energy size of the frequency that observation post need detect is to determine whether this frequency exists;
Unit during one batch total is connected with this detecting unit, to carry out time counting at signal;
One group of matching unit is connected with this timing unit respectively respectively, mates with signal and the standard No. model that will be received, and drops within the range of tolerable variance as the result system of coupling, thinks that then a certain telephone signal is detected, otherwise, then think not this signal;
One comprehensive unit, be connected with this group matching unit, the output of comprehensive each road signal, can not only detect the signal of existence, and can detect these signals and when finish, and export the code of detected coherent signal according to comprehensive each road signal judgment result, this comprehensive unit also is connected with this signal output coder, by this signal output coder the signal that is detected is exported.
7. use digital signal processor as claimed in claim 6 detects various telephone signals and carries out the chip of data communication, it is characterized in that, the computational methods of this discrete Fourier transform unit can be used 256 point quick Fourier conversion.
8. use digital signal processor as claimed in claim 6 detects various telephone signals and carries out the chip of data communication, it is characterized in that, be provided with a threshold value in this detecting unit, energy as frequency is higher than this threshold value, can think that then this frequency exists, otherwise, think that then this frequency does not exist.
9. use digital signal processor as claimed in claim 8 detects various telephone signals and carries out the chip of data communication, it is characterized in that, this threshold value must be determined via experiment, and when detecting, need to consider two frequencies that all exist as two frequencies, then this signal exists, do not exist if any a frequency, then this signal does not exist.
10. use digital signal processor as claimed in claim 6 detects various telephone signals and carries out the chip of data communication, it is characterized in that, after discrete Fourier transform calculating, be distributed in the signal output on the frequency domain, if one or more frequencies exist, then this signal exists at the unit time memory, and increase by 1 unit with the existing timing unit of signal this moment, otherwise the timing unit that signal is not existed increases by 1 unit.
11. use digital signal processor as claimed in claim 10 detects various telephone signals and carries out the chip of data communication, it is characterized in that this unit interval can be 10ms.
12. use digital signal processor as claimed in claim 8 detects various telephone signals and carries out the chip of data communication, it is characterized in that these codes can be defined voluntarily by the user.
13. use digital signal processor as claimed in claim 6 detects various telephone signals and carries out the chip of data communication, it is characterized in that, this data input cell is connected with a zero-crossing rate computing unit in addition, zero-crossing rate with signal calculated, make separately, reach the purpose of differentiation " 0 " or " 1 " two frequency zones.
14. use digital signal processor as claimed in claim 13 detects various telephone signals and carries out the chip of data communication, it is characterized in that the zero-crossing rate computing unit is connected with a time counting unit, make result by zero-crossing rate respectively to two frequency countings, to obtain their distribution situations on time-domain.
15. use digital signal processor as claimed in claim 14 detects various telephone signals and carries out the chip of data communication, it is characterized in that, this time counting unit partly is connected with a logic determines, by calculating two distributions of frequency on time-domain, convert thereof into logical zero and logical one.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN96111377A CN1062697C (en) | 1996-09-05 | 1996-09-05 | Chip for detecting telephone signals with digital signal processor and performing digital communication |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN96111377A CN1062697C (en) | 1996-09-05 | 1996-09-05 | Chip for detecting telephone signals with digital signal processor and performing digital communication |
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| Publication Number | Publication Date |
|---|---|
| CN1147740A true CN1147740A (en) | 1997-04-16 |
| CN1062697C CN1062697C (en) | 2001-02-28 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN96111377A Expired - Fee Related CN1062697C (en) | 1996-09-05 | 1996-09-05 | Chip for detecting telephone signals with digital signal processor and performing digital communication |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102201872A (en) * | 2010-03-22 | 2011-09-28 | 吴佳欣 | Low-power-consumption underwater acoustic communication arousing equipment |
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| CN2080269U (en) * | 1989-09-30 | 1991-07-03 | 湖南省零陵地区专利实验工厂 | Compactible detect double voice multi-frequency/pulse telephone set |
| CA2118552A1 (en) * | 1993-03-23 | 1994-09-24 | Edward M. Roney, Iv | Discrete audio frequency tone detection |
| CA2116043C (en) * | 1994-02-21 | 1997-09-23 | Alexander F. Tulai | Programmable digital call progress tone detector |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102201872A (en) * | 2010-03-22 | 2011-09-28 | 吴佳欣 | Low-power-consumption underwater acoustic communication arousing equipment |
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