CA2231826A1 - Method and system for the high-speed generation and transmission of a sequence of characters by means of voice frequencies - Google Patents
Method and system for the high-speed generation and transmission of a sequence of characters by means of voice frequencies Download PDFInfo
- Publication number
- CA2231826A1 CA2231826A1 CA002231826A CA2231826A CA2231826A1 CA 2231826 A1 CA2231826 A1 CA 2231826A1 CA 002231826 A CA002231826 A CA 002231826A CA 2231826 A CA2231826 A CA 2231826A CA 2231826 A1 CA2231826 A1 CA 2231826A1
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- Prior art keywords
- groups
- voice frequencies
- characters
- frequencies
- sequence
- Prior art date
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q1/00—Details of selecting apparatus or arrangements
- H04Q1/18—Electrical details
- H04Q1/30—Signalling arrangements; Manipulation of signalling currents
- H04Q1/44—Signalling arrangements; Manipulation of signalling currents using alternate current
- H04Q1/444—Signalling arrangements; Manipulation of signalling currents using alternate current with voice-band signalling frequencies
- H04Q1/45—Signalling arrangements; Manipulation of signalling currents using alternate current with voice-band signalling frequencies using multi-frequency signalling
- H04Q1/453—Signalling arrangements; Manipulation of signalling currents using alternate current with voice-band signalling frequencies using multi-frequency signalling in which m-out-of-n signalling frequencies are transmitted
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06Q—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR
- G06Q20/00—Payment architectures, schemes or protocols
- G06Q20/38—Payment protocols; Details thereof
- G06Q20/40—Authorisation, e.g. identification of payer or payee, verification of customer or shop credentials; Review and approval of payers, e.g. check credit lines or negative lists
- G06Q20/401—Transaction verification
- G06Q20/4012—Verifying personal identification numbers [PIN]
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/30—Systems using multi-frequency codes wherein each code element is represented by a combination of frequencies
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M1/00—Substation equipment, e.g. for use by subscribers
- H04M1/26—Devices for calling a subscriber
- H04M1/27—Devices whereby a plurality of signals may be stored simultaneously
- H04M1/274—Devices whereby a plurality of signals may be stored simultaneously with provision for storing more than one subscriber number at a time, e.g. using toothed disc
- H04M1/2745—Devices whereby a plurality of signals may be stored simultaneously with provision for storing more than one subscriber number at a time, e.g. using toothed disc using static electronic memories, e.g. chips
- H04M1/275—Devices whereby a plurality of signals may be stored simultaneously with provision for storing more than one subscriber number at a time, e.g. using toothed disc using static electronic memories, e.g. chips implemented by means of portable electronic directories
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M1/00—Substation equipment, e.g. for use by subscribers
- H04M1/26—Devices for calling a subscriber
- H04M1/30—Devices which can set up and transmit only one digit at a time
- H04M1/50—Devices which can set up and transmit only one digit at a time by generating or selecting currents of predetermined frequencies or combinations of frequencies
- H04M1/505—Devices which can set up and transmit only one digit at a time by generating or selecting currents of predetermined frequencies or combinations of frequencies signals generated in digital form
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M11/00—Telephonic communication systems specially adapted for combination with other electrical systems
- H04M11/06—Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors
- H04M11/066—Telephone sets adapted for data transmision
Abstract
A method for generating and rapidly transmitting a multi-character sequence using voice frequencies, wherein blanks between two adjacent characters are deleted during transmission when said characters are different or differently encoded.
Description
METHOD AND SYSTEM FOR THE HIGH-SPEED GENERATION AND
TRANSMISSION OF A SEQUENCE OF CHARACTERS BY MEANS OF VOICE
FREQUENCIES
The field of the invention is that of the transmission of data on a telephone network.
More specifically, the invention relates to a method and a system enabling the generation, by means of voice frequencies, of a sequence of characters and the high-speed tr~ncmicsion of these characters.
In the present description, the term "sequence of characters" is understood to mean a sequence of at least two characters, especially but not exclusively a telephone number, an iden~ c~ion code or enciphering data elements.
The invention has many applications. Thus, the method and system according to the invention may be used to secure long-distance electronic transactions, especially those pertaining to telephone services for which it is essential to be able to speedily identify the provider of the telephone service. It can be applied more particularly when the long-distance electronic transactions are secured by means of portable objects having a credit card format, sending out voice signals and designed to be used in combination with telephone receivers.
Conventionally, the multi-frequency encoding used to transmit dialling, identification and enciphering information on a telephone network is a dual tonemulti-frequency or DTMF encoding.
With this DTMF encoding, each character is encoded in the form of a combination of two frequencies (a high frequency and a low frequency) that are tr~n~mitted ~imull~neously. Each of the two frequencies transmitted is chosen from amongst two groups of four frequencies (namely a group of four low frequencies and a group of four high frequencies). One of the frequencies is chosen from one of the groups and the other frequency is chosen from the other group. It is thus possible to encode 4 x 4 = 16 different characters, i.e. generally the ten digits from 0 to 9 and six -additional characters. Owing to the fact that they are located in the telephone passband (from 100 to 3300 Hz), these frequencies are generally called voice or acoustic frequencies. They enable the tr~n~mic~ion of the telephone number of the called party and generally, in a conversation stage, of various other data elements (especially identifi~tion information). In general, DTMF encoding is implemented by means of a multi-frequency keyboard of a telephone set. The user enters the sequence of characters (for example the digits of a telephone number) by means of his keyboard.
Each stroke on this keyboard enables the encoding and dispatch of one character.There is also a known way of using DTMF encoding in a portable object (for example with a credit card format or in the form of tokens or pocket calculators) of the type designed to be used in combination with a telephone set. In this case, the user applies his portable object against the telephone set, and then activates it (for example by pressing a button designed for this purpose). The portable object then automatically enters a sequence of characters such as for example an identific~tion key designed to be verified by a vocal server which is at the called number.
In general, DTMF encoding enables the transmission of data elements at a speed of 4 to 8 characters per second. While this speed is generally enough for the transmission of ~ lling information, it is not so for all information elements and especially for the identification codes. Indeed, the number of characters that may be contained in an identification code is sometimes fairly great. Owing to the low speed of tr~n~mi~ion, the tr~n~mi~ion time is then extremely (and excessively) long for normal use by a private party.
As will be seen with reference to Figures 1 to 4 which describe the essential characteristics of DTMF tr:~n~mi~ion, it is necessary to set up a blank between the transmission of two successive characters. Indeed, when two successive characters are identical, the two DTMF frequencies used to encode this character are the same.
Consequently, if a blank is not inserted between two identical successive characters, one of them may be lost at the time of the decoding. The existence of this blank, whose duration is comparable to the period of transmission of a character, reduces the theoretical speed of tr~n~mi~ion of the characters by half.
The patent application EP.AØ184 953 by Thomson CSF dated 18th June 1986 as well as the patent application DE A 3026 016 by Siemens dated 21st January 1982 disclose a method for the generation and transmission, by means of voice frequencies, of a sequence of signals in which the blanks between two successivesignals are elimin~te~l However, the document EP.AØ184 953 by Thomson CSF
dated 18th June 1986 does not relate to the transmission of DTMF signals, and its teaching cannot be transposed to them. Furthermore, neither the document EP.AØ184 953 by Thomson CSF dated 18th June 1986 nor the document DE A 30 26 016 by Siemens dated 21st January 1982 rules out the case where two successive characters could give rise to identical tr~n~mi~ions.
Thus, while Thomson CSF and Siemens show that it is possible to sent out sequences without blanks, they do not deal with the technical problem to which the present invention provides a solution, namely that of avoiding confusion or loss of information during the reception of two successive identical characters comprising no blanks.
According to the invention, this problem is resolved and the goal of increasing the speed of tr~nsmis~ion is achieved.
The method according to the invention makes it possible, by means of DTMF
type voice frequencies, to generate a sequence comprising several characters and to transmit this sequence remotely at high speed. Said sequence is transmitted by acoustic means between a portable object generating said sequence and the microphone of a terminal. The method comprises the step of the elimin~tion, during tr~n~mi~ion, of the blanks between two successive characters wherein, to make it possible to elimitl~te the blanks:
- two successive characters are encoded distinctly, prior to their trzln~mi~ion,when they are identical, - the reverse operation is performed, after tr~n~mi~ion, in order to obtain the origin~l sequence.
According to a preferred alternative embodiment:
- the characters are encoded by the simultaneous transmission of N voice frequencies (N being greater than or equal to 2), each chosen from a selection of N
groups of voice frequencies at a rate of, at the most, one frequency per group; said N
groups being selected from N+l groups of voice frequencies; the frequencies of each group being different from those of the other groups, - the N groups selected are alternated regularly among the N+l groups.
More particularly, when the characters to be tr~n~mitted are extracted from a matrix of the sixteen DTMF characters:
- the characters are encoded by the simultaneous tr~n~mi~ion of two voice frequencies, each chosen from two of the three groups (Gl, G2, G3) of four voicefrequencies at a rate of, at the most, one voice frequency chosen per group, thefrequencies of each group being different from those of the other groups, - the two groups selected {(Gl, G2) (G2, G3)} from the three groups (Gl, G2, G3) are alternated regularly.
Thus, a case where two successive characters are generated with the same voice frequencies is avoided. It is thus possible to transmit the characters one after the other without any interruption time. The speed of tr:~n~mi~ion is increased and in practice doubled. Preferably, said sequence belongs to the group comprising:
telephone numbers, identification codes and enciphering data.
The invention also relates to a system making it possible, by means of DTMF
type voice frequencies, to generate a sequence comprising several characters representing data elements and to transmit these data elements remotely at high speed, in elimin~ting the blanks between two successive characters. Said system consists of:
- a portable object tr:lncmitting DTMF type voice frequencies, designed to be used in combination with the microphone of a terminal, said portable object 4~
comprising means for the distinct encoding of two successive characters when they are identical, prior to their tr~n~mi.c.cion, - a computer interconnected to the terminal through a communications network, comprising means for the performance, after transmission, of the reverse decoding operation and for the reconstitution of the original sequence.
Preferably, the portable object comprises:
* means for the generation of N+l groups of voice frequencies, with N greater than or equal to 2, * means for the selection of N voice frequencies (with N greater than or equal to 2) each chosen from a selection of N groups of voice frequencies, at a rate of, at the most, one frequency per group, said N groups being selected from N+l groups of voice frequencies; the frequencies of each group being different from those of the other groups, * means enabling the alternation of the selections of N groups, * means for the simllltzlneous tr~nsmission of the N voice frequencies selected.The invention also pertains to a portable object tr~n~mitting DTMF type voice frequ~encies, designed to be used in combination with the microphone of a terrninal.
Said portable object comprises means for the distinct encoding of two successivecharacters when they are identical, prior to their tr~n.cmi.~ion on a communications network interconnected to the termin:~l Preferably, the portable object comprises:
* means for the generation of N+l groups of voice frequencies, with N greater than or equal to 2, * means for the selection of N voice frequencies (with N greater than or equal to 2) each chosen from a selection of N groups of voice frequencies, at a rate of, at the most, one frequency per group, said N groups being selected from N+l groups of voice frequencies; the frequencies of each group being different from those of the other groups, 4~6y~
* means enabling the alternation of the selections of N groups, * means for the ~imlllt:~neous tr~n~mi~ion of the N voice frequencies selected.
The invention also relates to a DTMF type multi-frequency terminal enabling a user to enter a sequence of characters to be transmitted on a telephone network. Said t~rmin~l comprises means for the distinct encoding of two successive characters when they are identical, prior to their transmission on a communications network interconnected to the termin~l Preferably, the terminal comprises:
* means for the generation of N+l groups of voice frequencies, with N greater than or equal to 2, * means for the selection of N voice frequencies (with N greater than or equal to 2) each chosen from a selection of N groups of voice frequencies, at a rate of, at the most, one frequency per group; said N groups being selected from N+l groups of voice frequencies; the frequencies of each group being dirr~ t from those of the other groups, * means enabling the alternation of the selections of N groups, * means for the simultaneous tr:~n~mi~ion of the N voice frequencies selected.
* mGan~ enablin~ the alternation of the combination~ of N ~roup~, * mo~n6 for tho ~imlllt~nnouE: tr~n~mi~ion of the N voice frequencieE s~le~tcd.
Other features and advantages of the invention shall appear from the following description of two preferred embodiments of the invention given by way of indicatory S and non-restrictive examples and from the appended drawings, of which:
- Flgure 1 shows an exemplary sequence of characters generated by means of voice frequencles;
- Figures 2 and 3 respectively show the two groups of voice frequencies used in the known DTMF encoding (Figure 2) and the corresponding encoding table (Figure 3);
- Figure 4 explains the generation of the sequence of Figure 1 when the known DTMF encoding is implemented;
- Figure 5 shows the two sets of groups of voice frequencies used in a particular embodiment of the method of the invention;
- Figure 6 shows the encoding table corresponding to the second set of groups oflS voice frequencies appealillg in Figure 5;
- Figure 7 explains the generation of the sequence of Figure 1 when the particular embodiment of the method of the invention is implemented;
- Figure 8 shows a simplified drawing of a particular embodiment of the multi-frequency encoding device; and - Figure 9 shows a simplified drawing of a particular embodiment of the system according to the invention.
The invention therefore relates to a method and system enabling the generation and tr~n~mic~ion, by means of voice frequencies, of a sequence of characters. A sequence of this kind is generally a telephone number, an identification code, or again an enciphering key. However, it is clear that the present invention can be applied to any type of sequence of characters.
Figure 1 shows an exemplary sequence of characters 1 generated by means of voicefrequencies, by a multi-frequency encoding device that is known or else the device of the invention. In this example, the first five characters of the sequence 1 are: "3", "*", "4", "#" and " 1".
Referring to Figures 2, 3 and 4, we shall now briefly recall the essential characteristics of the known DTMF encoding. As is shown in Figure 4, with the DTMF
encoding, each character ("3", "*", "4", etc.) of the sequence 1 is encoded in the form of a combination of two frequencies {f(Gl) + f(G2)}. In other words, a low frequency S f(Gl) and a high frequency f(G2) are tr~n~mittecl simultaneously so as to generate a character. Each of the two frequencies f(Gl), f(G2) tr:~n~mitte-l simultaneously is chosen from among two groups of four frequencies at a rate of, at the most, one frequency per group. As shown in Figure 2, these two groups are a group Gl of four low frequencies and a group of G2 of four high frequencies. It is thus possible to encode 4 x 4 = 16 different characters. The encoding table of these 16 characters is shown in Figure 3. It comprises the ten digits (0 to 9) and six additional characters (letters A to F), two special characters "*" and "#" being encoded in the same way as the letters A and B
respectivelyThe first character ("3") of the sequence 1 is preceded by a starting silence 2, then two successive characters are always separated by a silence 3.
The main principle of the invention consists of the generation of each character by the ~imlllt~neous transmission of N voice frequencies (with N greater than or equal to 2), choosing these N voice frequencies from among N+l groups of voice frequencies (while the DTMF encoding uses only two groups of voice frequencies), and then regularlyalternating the N groups selected from among the N+l groups.
If N is greater than 2, the number of different characters that can be encoded is increased with respect to DTMF.
Referring to Figures 5, 6 and 7, a description is now given of a particular mode of performing the method of the invention, in which N is equal to 2.
As shown in Figure 7, with this mode of perforrning the method of the invention,each character ("3, "*", "4", etc.) of the sequence 1 is encoded in the form of a combination of two frequencies {f(Gl) + f(G2)} or {f(G2) + f(G3)}. The two voicefrequencies f(Gl) and f(G2) or f(G2) and f(G3) are chosen from among the first, second and third groups of voice frequencies Gl, G2 and G3.
These groups of voice frequencies Gl, G2 and G3 are divided into two sets (cf.
table of Figure 5), namely a first set El comprising the first and second groups Gl, G2 and a second set E2 comprising the second and third groups G2, G3. The first andsecond groups Gl, G2 are for example the two groups of frequencies conventionally used in DTMF (the latter have already been presented here above in the context of the reminder of the DTMF encoding method). In this case, the third group G3 also comprises four voice frequencies.
The encoding table associated with the second set E2 is shown in Figure 6. This second set E2 associated with the first set E 1 is shown in Figure 2. It will be noted that these two tables of 16 characters are identical.
The two sets El and E2 are used alternately to generate two successive characters of the sequence 1. This enables the transmission of two successive characters, even if they are identical, without any intermediate silence. The standard transmission speed goes from 8 to 16 characters per second.
Referring to Figure 8, a description shall now be given of a particular embodiment of the multi-frequency encoding device. This device comprises:
lS - means 201, 202, 203 for the generation of three groups Gl, G2, G3 of voice frequencies, each group of voice frequencies comprising for example four voice frequencies;
- means 30 for the selection of two voice frequencies 22 from among, alternately, the two groups of voice frequencies El (Gl, G2) and E2 (G2, G3);
- means 40 for the cimlllt~neous tr~n~mi~ion of the two selected voice frequencies 22.
Figure 9 shows a simplified diagram of a particular embodiment of the system according to the invention. The system according to the invention consists of:
- a portable object 50 tr:~ncmitting voice frequencies (as described with reference to Figure 8) designed to be used in combination with the microphone 60 of a terminal 70 (telephone set, mllltim~ computer), said portable object comprising:
* means 20 for the generation of N+l groups of voice frequencies, with N greaterthan or equal to 2 (N = 2 in the case of Figure 8), * means 30 for the selection of N voice frequencies, each chosen from among the N+l groups of voice frequencies at a rate of, at the most, one voice frequency per group, * means 30 enabling the alternation of the combinations of N groups, * means 40 for the simlllt~n~ous tr~nsmi~ion of N selected voiee frequencies, - a eommunications network 80 enabling the characters representing the data elements to be tr~n~mitt(~1 from the microphone of the telephone set to a distant computer, - a computer 90 comprising means 100 enabling the reconstitution of the originalsequence of characters and the processing of said sequence.
It is elear that the first set El may comprise the first and second group Gl, G2 and that the second set E2 may comprise the groups G2 and G3 or Gl and G3.
It is also elear that those skilled in the art will easily be able to broaden the seope of this description to other cases and especially to the case where N = 4 (with five groups in all and four frequencies tr~n~mitte~l simlllt~neously to encode a character). Consequently, the speed of transmission may be further increased if there are reception devices tuned both to these voice frequeneies and to these tr~n~mi~ion speeds.
The method and the system according to the invention can be implemented especially in a portable object as described here above. They may also be implemented in a multi-frequency terminal enabling a user to enter a sequence of characters (to be tr~nsmitte~l on the telephone network).
In order to eliminzlte the blanks (or intermediate silences) and in order to increase the speed of tr~nsmission of characters, two variants have also been envisaged.
According to the first variant, two successive characters are transmitted with an intermediate silence only if they are identical; Whenever they are different, the two sueeessive eharacters are tr~ncmitted without intermediate silenee.
According to the second variant, the multi-frequency encoding proper is preceded by a processing step (function F) so as to prevent two successive characters of the frequency from being identical. At reception, the multi-frequency decoding is followed by a processing step in reverse to the previous one (function F-l). It is within the range of those skilled in the art to choose and implement processing operators F and F-l such as these to obtain a result of this kind.
TRANSMISSION OF A SEQUENCE OF CHARACTERS BY MEANS OF VOICE
FREQUENCIES
The field of the invention is that of the transmission of data on a telephone network.
More specifically, the invention relates to a method and a system enabling the generation, by means of voice frequencies, of a sequence of characters and the high-speed tr~ncmicsion of these characters.
In the present description, the term "sequence of characters" is understood to mean a sequence of at least two characters, especially but not exclusively a telephone number, an iden~ c~ion code or enciphering data elements.
The invention has many applications. Thus, the method and system according to the invention may be used to secure long-distance electronic transactions, especially those pertaining to telephone services for which it is essential to be able to speedily identify the provider of the telephone service. It can be applied more particularly when the long-distance electronic transactions are secured by means of portable objects having a credit card format, sending out voice signals and designed to be used in combination with telephone receivers.
Conventionally, the multi-frequency encoding used to transmit dialling, identification and enciphering information on a telephone network is a dual tonemulti-frequency or DTMF encoding.
With this DTMF encoding, each character is encoded in the form of a combination of two frequencies (a high frequency and a low frequency) that are tr~n~mitted ~imull~neously. Each of the two frequencies transmitted is chosen from amongst two groups of four frequencies (namely a group of four low frequencies and a group of four high frequencies). One of the frequencies is chosen from one of the groups and the other frequency is chosen from the other group. It is thus possible to encode 4 x 4 = 16 different characters, i.e. generally the ten digits from 0 to 9 and six -additional characters. Owing to the fact that they are located in the telephone passband (from 100 to 3300 Hz), these frequencies are generally called voice or acoustic frequencies. They enable the tr~n~mic~ion of the telephone number of the called party and generally, in a conversation stage, of various other data elements (especially identifi~tion information). In general, DTMF encoding is implemented by means of a multi-frequency keyboard of a telephone set. The user enters the sequence of characters (for example the digits of a telephone number) by means of his keyboard.
Each stroke on this keyboard enables the encoding and dispatch of one character.There is also a known way of using DTMF encoding in a portable object (for example with a credit card format or in the form of tokens or pocket calculators) of the type designed to be used in combination with a telephone set. In this case, the user applies his portable object against the telephone set, and then activates it (for example by pressing a button designed for this purpose). The portable object then automatically enters a sequence of characters such as for example an identific~tion key designed to be verified by a vocal server which is at the called number.
In general, DTMF encoding enables the transmission of data elements at a speed of 4 to 8 characters per second. While this speed is generally enough for the transmission of ~ lling information, it is not so for all information elements and especially for the identification codes. Indeed, the number of characters that may be contained in an identification code is sometimes fairly great. Owing to the low speed of tr~n~mi~ion, the tr~n~mi~ion time is then extremely (and excessively) long for normal use by a private party.
As will be seen with reference to Figures 1 to 4 which describe the essential characteristics of DTMF tr:~n~mi~ion, it is necessary to set up a blank between the transmission of two successive characters. Indeed, when two successive characters are identical, the two DTMF frequencies used to encode this character are the same.
Consequently, if a blank is not inserted between two identical successive characters, one of them may be lost at the time of the decoding. The existence of this blank, whose duration is comparable to the period of transmission of a character, reduces the theoretical speed of tr~n~mi~ion of the characters by half.
The patent application EP.AØ184 953 by Thomson CSF dated 18th June 1986 as well as the patent application DE A 3026 016 by Siemens dated 21st January 1982 disclose a method for the generation and transmission, by means of voice frequencies, of a sequence of signals in which the blanks between two successivesignals are elimin~te~l However, the document EP.AØ184 953 by Thomson CSF
dated 18th June 1986 does not relate to the transmission of DTMF signals, and its teaching cannot be transposed to them. Furthermore, neither the document EP.AØ184 953 by Thomson CSF dated 18th June 1986 nor the document DE A 30 26 016 by Siemens dated 21st January 1982 rules out the case where two successive characters could give rise to identical tr~n~mi~ions.
Thus, while Thomson CSF and Siemens show that it is possible to sent out sequences without blanks, they do not deal with the technical problem to which the present invention provides a solution, namely that of avoiding confusion or loss of information during the reception of two successive identical characters comprising no blanks.
According to the invention, this problem is resolved and the goal of increasing the speed of tr~nsmis~ion is achieved.
The method according to the invention makes it possible, by means of DTMF
type voice frequencies, to generate a sequence comprising several characters and to transmit this sequence remotely at high speed. Said sequence is transmitted by acoustic means between a portable object generating said sequence and the microphone of a terminal. The method comprises the step of the elimin~tion, during tr~n~mi~ion, of the blanks between two successive characters wherein, to make it possible to elimitl~te the blanks:
- two successive characters are encoded distinctly, prior to their trzln~mi~ion,when they are identical, - the reverse operation is performed, after tr~n~mi~ion, in order to obtain the origin~l sequence.
According to a preferred alternative embodiment:
- the characters are encoded by the simultaneous transmission of N voice frequencies (N being greater than or equal to 2), each chosen from a selection of N
groups of voice frequencies at a rate of, at the most, one frequency per group; said N
groups being selected from N+l groups of voice frequencies; the frequencies of each group being different from those of the other groups, - the N groups selected are alternated regularly among the N+l groups.
More particularly, when the characters to be tr~n~mitted are extracted from a matrix of the sixteen DTMF characters:
- the characters are encoded by the simultaneous tr~n~mi~ion of two voice frequencies, each chosen from two of the three groups (Gl, G2, G3) of four voicefrequencies at a rate of, at the most, one voice frequency chosen per group, thefrequencies of each group being different from those of the other groups, - the two groups selected {(Gl, G2) (G2, G3)} from the three groups (Gl, G2, G3) are alternated regularly.
Thus, a case where two successive characters are generated with the same voice frequencies is avoided. It is thus possible to transmit the characters one after the other without any interruption time. The speed of tr:~n~mi~ion is increased and in practice doubled. Preferably, said sequence belongs to the group comprising:
telephone numbers, identification codes and enciphering data.
The invention also relates to a system making it possible, by means of DTMF
type voice frequencies, to generate a sequence comprising several characters representing data elements and to transmit these data elements remotely at high speed, in elimin~ting the blanks between two successive characters. Said system consists of:
- a portable object tr:lncmitting DTMF type voice frequencies, designed to be used in combination with the microphone of a terminal, said portable object 4~
comprising means for the distinct encoding of two successive characters when they are identical, prior to their tr~n~mi.c.cion, - a computer interconnected to the terminal through a communications network, comprising means for the performance, after transmission, of the reverse decoding operation and for the reconstitution of the original sequence.
Preferably, the portable object comprises:
* means for the generation of N+l groups of voice frequencies, with N greater than or equal to 2, * means for the selection of N voice frequencies (with N greater than or equal to 2) each chosen from a selection of N groups of voice frequencies, at a rate of, at the most, one frequency per group, said N groups being selected from N+l groups of voice frequencies; the frequencies of each group being different from those of the other groups, * means enabling the alternation of the selections of N groups, * means for the simllltzlneous tr~nsmission of the N voice frequencies selected.The invention also pertains to a portable object tr~n~mitting DTMF type voice frequ~encies, designed to be used in combination with the microphone of a terrninal.
Said portable object comprises means for the distinct encoding of two successivecharacters when they are identical, prior to their tr~n.cmi.~ion on a communications network interconnected to the termin:~l Preferably, the portable object comprises:
* means for the generation of N+l groups of voice frequencies, with N greater than or equal to 2, * means for the selection of N voice frequencies (with N greater than or equal to 2) each chosen from a selection of N groups of voice frequencies, at a rate of, at the most, one frequency per group, said N groups being selected from N+l groups of voice frequencies; the frequencies of each group being different from those of the other groups, 4~6y~
* means enabling the alternation of the selections of N groups, * means for the ~imlllt:~neous tr~n~mi~ion of the N voice frequencies selected.
The invention also relates to a DTMF type multi-frequency terminal enabling a user to enter a sequence of characters to be transmitted on a telephone network. Said t~rmin~l comprises means for the distinct encoding of two successive characters when they are identical, prior to their transmission on a communications network interconnected to the termin~l Preferably, the terminal comprises:
* means for the generation of N+l groups of voice frequencies, with N greater than or equal to 2, * means for the selection of N voice frequencies (with N greater than or equal to 2) each chosen from a selection of N groups of voice frequencies, at a rate of, at the most, one frequency per group; said N groups being selected from N+l groups of voice frequencies; the frequencies of each group being dirr~ t from those of the other groups, * means enabling the alternation of the selections of N groups, * means for the simultaneous tr:~n~mi~ion of the N voice frequencies selected.
* mGan~ enablin~ the alternation of the combination~ of N ~roup~, * mo~n6 for tho ~imlllt~nnouE: tr~n~mi~ion of the N voice frequencieE s~le~tcd.
Other features and advantages of the invention shall appear from the following description of two preferred embodiments of the invention given by way of indicatory S and non-restrictive examples and from the appended drawings, of which:
- Flgure 1 shows an exemplary sequence of characters generated by means of voice frequencles;
- Figures 2 and 3 respectively show the two groups of voice frequencies used in the known DTMF encoding (Figure 2) and the corresponding encoding table (Figure 3);
- Figure 4 explains the generation of the sequence of Figure 1 when the known DTMF encoding is implemented;
- Figure 5 shows the two sets of groups of voice frequencies used in a particular embodiment of the method of the invention;
- Figure 6 shows the encoding table corresponding to the second set of groups oflS voice frequencies appealillg in Figure 5;
- Figure 7 explains the generation of the sequence of Figure 1 when the particular embodiment of the method of the invention is implemented;
- Figure 8 shows a simplified drawing of a particular embodiment of the multi-frequency encoding device; and - Figure 9 shows a simplified drawing of a particular embodiment of the system according to the invention.
The invention therefore relates to a method and system enabling the generation and tr~n~mic~ion, by means of voice frequencies, of a sequence of characters. A sequence of this kind is generally a telephone number, an identification code, or again an enciphering key. However, it is clear that the present invention can be applied to any type of sequence of characters.
Figure 1 shows an exemplary sequence of characters 1 generated by means of voicefrequencies, by a multi-frequency encoding device that is known or else the device of the invention. In this example, the first five characters of the sequence 1 are: "3", "*", "4", "#" and " 1".
Referring to Figures 2, 3 and 4, we shall now briefly recall the essential characteristics of the known DTMF encoding. As is shown in Figure 4, with the DTMF
encoding, each character ("3", "*", "4", etc.) of the sequence 1 is encoded in the form of a combination of two frequencies {f(Gl) + f(G2)}. In other words, a low frequency S f(Gl) and a high frequency f(G2) are tr~n~mittecl simultaneously so as to generate a character. Each of the two frequencies f(Gl), f(G2) tr:~n~mitte-l simultaneously is chosen from among two groups of four frequencies at a rate of, at the most, one frequency per group. As shown in Figure 2, these two groups are a group Gl of four low frequencies and a group of G2 of four high frequencies. It is thus possible to encode 4 x 4 = 16 different characters. The encoding table of these 16 characters is shown in Figure 3. It comprises the ten digits (0 to 9) and six additional characters (letters A to F), two special characters "*" and "#" being encoded in the same way as the letters A and B
respectivelyThe first character ("3") of the sequence 1 is preceded by a starting silence 2, then two successive characters are always separated by a silence 3.
The main principle of the invention consists of the generation of each character by the ~imlllt~neous transmission of N voice frequencies (with N greater than or equal to 2), choosing these N voice frequencies from among N+l groups of voice frequencies (while the DTMF encoding uses only two groups of voice frequencies), and then regularlyalternating the N groups selected from among the N+l groups.
If N is greater than 2, the number of different characters that can be encoded is increased with respect to DTMF.
Referring to Figures 5, 6 and 7, a description is now given of a particular mode of performing the method of the invention, in which N is equal to 2.
As shown in Figure 7, with this mode of perforrning the method of the invention,each character ("3, "*", "4", etc.) of the sequence 1 is encoded in the form of a combination of two frequencies {f(Gl) + f(G2)} or {f(G2) + f(G3)}. The two voicefrequencies f(Gl) and f(G2) or f(G2) and f(G3) are chosen from among the first, second and third groups of voice frequencies Gl, G2 and G3.
These groups of voice frequencies Gl, G2 and G3 are divided into two sets (cf.
table of Figure 5), namely a first set El comprising the first and second groups Gl, G2 and a second set E2 comprising the second and third groups G2, G3. The first andsecond groups Gl, G2 are for example the two groups of frequencies conventionally used in DTMF (the latter have already been presented here above in the context of the reminder of the DTMF encoding method). In this case, the third group G3 also comprises four voice frequencies.
The encoding table associated with the second set E2 is shown in Figure 6. This second set E2 associated with the first set E 1 is shown in Figure 2. It will be noted that these two tables of 16 characters are identical.
The two sets El and E2 are used alternately to generate two successive characters of the sequence 1. This enables the transmission of two successive characters, even if they are identical, without any intermediate silence. The standard transmission speed goes from 8 to 16 characters per second.
Referring to Figure 8, a description shall now be given of a particular embodiment of the multi-frequency encoding device. This device comprises:
lS - means 201, 202, 203 for the generation of three groups Gl, G2, G3 of voice frequencies, each group of voice frequencies comprising for example four voice frequencies;
- means 30 for the selection of two voice frequencies 22 from among, alternately, the two groups of voice frequencies El (Gl, G2) and E2 (G2, G3);
- means 40 for the cimlllt~neous tr~n~mi~ion of the two selected voice frequencies 22.
Figure 9 shows a simplified diagram of a particular embodiment of the system according to the invention. The system according to the invention consists of:
- a portable object 50 tr:~ncmitting voice frequencies (as described with reference to Figure 8) designed to be used in combination with the microphone 60 of a terminal 70 (telephone set, mllltim~ computer), said portable object comprising:
* means 20 for the generation of N+l groups of voice frequencies, with N greaterthan or equal to 2 (N = 2 in the case of Figure 8), * means 30 for the selection of N voice frequencies, each chosen from among the N+l groups of voice frequencies at a rate of, at the most, one voice frequency per group, * means 30 enabling the alternation of the combinations of N groups, * means 40 for the simlllt~n~ous tr~nsmi~ion of N selected voiee frequencies, - a eommunications network 80 enabling the characters representing the data elements to be tr~n~mitt(~1 from the microphone of the telephone set to a distant computer, - a computer 90 comprising means 100 enabling the reconstitution of the originalsequence of characters and the processing of said sequence.
It is elear that the first set El may comprise the first and second group Gl, G2 and that the second set E2 may comprise the groups G2 and G3 or Gl and G3.
It is also elear that those skilled in the art will easily be able to broaden the seope of this description to other cases and especially to the case where N = 4 (with five groups in all and four frequencies tr~n~mitte~l simlllt~neously to encode a character). Consequently, the speed of transmission may be further increased if there are reception devices tuned both to these voice frequeneies and to these tr~n~mi~ion speeds.
The method and the system according to the invention can be implemented especially in a portable object as described here above. They may also be implemented in a multi-frequency terminal enabling a user to enter a sequence of characters (to be tr~nsmitte~l on the telephone network).
In order to eliminzlte the blanks (or intermediate silences) and in order to increase the speed of tr~nsmission of characters, two variants have also been envisaged.
According to the first variant, two successive characters are transmitted with an intermediate silence only if they are identical; Whenever they are different, the two sueeessive eharacters are tr~ncmitted without intermediate silenee.
According to the second variant, the multi-frequency encoding proper is preceded by a processing step (function F) so as to prevent two successive characters of the frequency from being identical. At reception, the multi-frequency decoding is followed by a processing step in reverse to the previous one (function F-l). It is within the range of those skilled in the art to choose and implement processing operators F and F-l such as these to obtain a result of this kind.
Claims (10)
1. A method enabling the generation, by means of DTMF type voice frequencies, of a sequence comprising several characters and the transmission of this sequence remotely at high speed, said sequence being transmitted by acoustic means between a portable object generating said sequence and the microphone of a terminal, said method comprising the step of the elimination, during transmission, of the blanks between two successive characters wherein, according to said method, to make it possible to eliminate the blanks:
- two successive characters are encoded distinctly, prior to their transmission,when they are identical, - the reverse operation is performed, after transmission, in order to obtain theoriginal sequence.
- two successive characters are encoded distinctly, prior to their transmission,when they are identical, - the reverse operation is performed, after transmission, in order to obtain theoriginal sequence.
2. A method according to claim 1, wherein:
- the characters are encoded by the simultaneous transmission of N voice frequencies (N being greater than or equal to 2), each chosen from a selection of N
groups of voice frequencies at a rate of, at the most, one frequency per group; said N
groups being selected from N+1 groups of voice frequencies; the frequencies of each group being different from those of the other groups, - the N groups selected are alternated regularly among the N+1 groups.
- the characters are encoded by the simultaneous transmission of N voice frequencies (N being greater than or equal to 2), each chosen from a selection of N
groups of voice frequencies at a rate of, at the most, one frequency per group; said N
groups being selected from N+1 groups of voice frequencies; the frequencies of each group being different from those of the other groups, - the N groups selected are alternated regularly among the N+1 groups.
3. A method according to claim 2, the characters to be transmitted being extracted from a matrix of the sixteen DTMF characters, wherein:
- the characters are encoded by the simultaneous transmission of two voice frequencies, each chosen from two of the three groups (G1, G2, G3) of four voicefrequencies at a rate of, at the most, one voice frequency chosen per group, thefrequencies of each group being different from those of the other groups, - the two groups selected {(G1, G2) (G2, G3)} from the three groups (G1, G2, G3) are alternated regularly.
- the characters are encoded by the simultaneous transmission of two voice frequencies, each chosen from two of the three groups (G1, G2, G3) of four voicefrequencies at a rate of, at the most, one voice frequency chosen per group, thefrequencies of each group being different from those of the other groups, - the two groups selected {(G1, G2) (G2, G3)} from the three groups (G1, G2, G3) are alternated regularly.
4. A method according to any of the claims 1, 2 or 3, wherein the sequence of several characters belongs to the group comprising:
- telephone numbers, - identification codes, - encryption data.
- telephone numbers, - identification codes, - encryption data.
5. A system enabling the generation, by means of DTMF type voice frequencies, of a sequence comprising several characters representing data elements and the transmission of these data elements remotely at high speed, in eliminating the blanks between two successive characters, wherein said system consists of:
- a portable object transmitting DTMF type voice frequencies, designed to be used in combination with the microphone of a terminal, said portable object comprising means for the distinct encoding of two successive characters when they are identical, prior to their transmission, - a computer interconnected to the terminal through a communications network, comprising means for the performance, after transmission, of the reverse decoding operation and for the reconstitution of the original sequence.
- a portable object transmitting DTMF type voice frequencies, designed to be used in combination with the microphone of a terminal, said portable object comprising means for the distinct encoding of two successive characters when they are identical, prior to their transmission, - a computer interconnected to the terminal through a communications network, comprising means for the performance, after transmission, of the reverse decoding operation and for the reconstitution of the original sequence.
6. A system according to claim 5, said portable object comprising:
* means for the generation of N+1 groups of voice frequencies, with N greater than or equal to 2, * means for the selection of N voice frequencies (with N greater than or equal to 2) each chosen from a selection of N groups of voice frequencies, at a rate of, at the most, one frequency per group, said N groups being selected from N+1 groups of voice frequencies; the frequencies of each group being different from those of the other groups, * means enabling the alternation of the selections of N groups, * means for the simultaneous transmission of the N voice frequencies selected.
* means for the generation of N+1 groups of voice frequencies, with N greater than or equal to 2, * means for the selection of N voice frequencies (with N greater than or equal to 2) each chosen from a selection of N groups of voice frequencies, at a rate of, at the most, one frequency per group, said N groups being selected from N+1 groups of voice frequencies; the frequencies of each group being different from those of the other groups, * means enabling the alternation of the selections of N groups, * means for the simultaneous transmission of the N voice frequencies selected.
7. A portable object transmitting DTMF type voice frequencies, designed to be used in combination with a microphone of a terminal, said portable object comprising means for the distinct encoding of two successive characters when they are identical, prior to their transmission on a communications network interconnected to the terminal.
8. A portable object according to claim 7, said portable object comprising:
* means for the generation of N+1 groups of voice frequencies, with N greater than or equal to 2, * means for the selection of N voice frequencies (with N greater than or equal to 2) each chosen from a selection of N groups of voice frequencies, at a rate of, at the most, one frequency per group, said N groups being selected from N+1 groups of voice frequencies; the frequencies of each group being different from those of the other groups, * means enabling the alternation of the selections of N groups, * means for the simultaneous transmission of the N voice frequencies selected.
* means for the generation of N+1 groups of voice frequencies, with N greater than or equal to 2, * means for the selection of N voice frequencies (with N greater than or equal to 2) each chosen from a selection of N groups of voice frequencies, at a rate of, at the most, one frequency per group, said N groups being selected from N+1 groups of voice frequencies; the frequencies of each group being different from those of the other groups, * means enabling the alternation of the selections of N groups, * means for the simultaneous transmission of the N voice frequencies selected.
9. A DTMF type multi-frequency terminal enabling a user to enter a sequence of characters to be transmitted on a telephone network, said terminal comprising means for the distinct encoding of two successive characters when they are identical, prior to their transmission on a communications network interconnected to the terminal.
10. A terminal according to claim 9, comprising:
* means for the generation of N+1 groups of voice frequencies, with N greater than or equal to 2, * means for the selection of N voice frequencies (with N greater than or equal to 2), each chosen from a selection of N groups of voice frequencies, at a rate of, at the most, one frequency per group; said N groups being selected from N+1 groups of voice frequencies; the frequencies of each group being different from those of the other groups, * means enabling the alternation of the selections of N groups, * means for the simultaneous transmission of the N voice frequencies selected.
* means for the generation of N+1 groups of voice frequencies, with N greater than or equal to 2, * means for the selection of N voice frequencies (with N greater than or equal to 2), each chosen from a selection of N groups of voice frequencies, at a rate of, at the most, one frequency per group; said N groups being selected from N+1 groups of voice frequencies; the frequencies of each group being different from those of the other groups, * means enabling the alternation of the selections of N groups, * means for the simultaneous transmission of the N voice frequencies selected.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR9511414A FR2739238B1 (en) | 1995-09-25 | 1995-09-25 | ASYNCHRONOUS ACOUSTIC CODING BASED ON SIMULTANEOUS FREQUENCY GROUPS |
| FR9511414 | 1995-09-25 |
Publications (1)
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|---|---|
| CA2231826A1 true CA2231826A1 (en) | 1997-04-03 |
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| CA002231826A Abandoned CA2231826A1 (en) | 1995-09-25 | 1996-09-25 | Method and system for the high-speed generation and transmission of a sequence of characters by means of voice frequencies |
Country Status (17)
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| US (1) | US5859913A (en) |
| EP (1) | EP0852867B1 (en) |
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| AT (1) | ATE202247T1 (en) |
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| IL125221A0 (en) | 1998-07-06 | 1999-03-12 | Toy Control Ltd | Motion activation using passive sound source |
| US6101401A (en) * | 1998-08-26 | 2000-08-08 | Dbtel Incorporated | Wireless telephone dialing method |
| IL127569A0 (en) * | 1998-09-16 | 1999-10-28 | Comsense Technologies Ltd | Interactive toys |
| US6607136B1 (en) * | 1998-09-16 | 2003-08-19 | Beepcard Inc. | Physical presence digital authentication system |
| CA2345745A1 (en) | 1998-10-02 | 2000-04-13 | Comsense Technologies, Ltd. | Card for interaction with a computer |
| US8019609B2 (en) * | 1999-10-04 | 2011-09-13 | Dialware Inc. | Sonic/ultrasonic authentication method |
| US7280970B2 (en) * | 1999-10-04 | 2007-10-09 | Beepcard Ltd. | Sonic/ultrasonic authentication device |
| WO2002029658A1 (en) * | 2000-09-30 | 2002-04-11 | Sega Corporation | Service ticket issuing system and service ticket issuing service |
| US9219708B2 (en) * | 2001-03-22 | 2015-12-22 | DialwareInc. | Method and system for remotely authenticating identification devices |
| US8447668B2 (en) | 2004-01-16 | 2013-05-21 | Keith Jentoft | Audio-equipped transaction card systems and approaches |
| US8266441B2 (en) * | 2005-04-22 | 2012-09-11 | Bank Of America Corporation | One-time password credit/debit card |
| US9251637B2 (en) | 2006-11-15 | 2016-02-02 | Bank Of America Corporation | Method and apparatus for using at least a portion of a one-time password as a dynamic card verification value |
| US8002193B2 (en) | 2007-03-12 | 2011-08-23 | Visa U.S.A. Inc. | Payment card dynamically receiving power from external source |
| US20160108723A1 (en) * | 2014-10-21 | 2016-04-21 | Alkhorayef Petroleum Company | Systems and Methods of Communication Signal Processing For Downhole Applications |
| US10574650B2 (en) | 2017-05-17 | 2020-02-25 | Bank Of America Corporation | System for electronic authentication with live user determination |
| US10387632B2 (en) | 2017-05-17 | 2019-08-20 | Bank Of America Corporation | System for provisioning and allowing secure access to a virtual credential |
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|---|---|---|---|---|
| US4313207A (en) * | 1967-02-10 | 1982-01-26 | The United States Of America As Represented By The Secretary Of The Air Force | Method and system for selectively disrupting radio telegraph communications |
| US3582895A (en) * | 1969-01-15 | 1971-06-01 | Ibm | Alphanumeric parallel tone, sequential character system, method, and apparatus |
| US3810019A (en) * | 1972-09-25 | 1974-05-07 | Sperry Rand Corp | Multifrequency communication system for fading channels |
| US4126768A (en) * | 1977-06-27 | 1978-11-21 | Bell Telephone Laboratories, Incorporated | Portable automatic number outpulser |
| DE3026016C2 (en) * | 1980-07-09 | 1984-12-13 | Siemens AG, 1000 Berlin und 8000 München | Circuit arrangement for demodulating mixed frequencies received at a central station |
| JPS60141033A (en) * | 1983-12-28 | 1985-07-26 | Nec Corp | Acoustic coupler |
| FR2573596B1 (en) * | 1984-11-16 | 1987-01-16 | Thomson Csf | METHOD AND DEVICE FOR TRANSMITTING DIGITAL INFORMATION BY DIFFERENTIAL FREQUENCY MOVEMENT |
| US4817135A (en) * | 1987-11-24 | 1989-03-28 | U.S. News Limited Partnership | CRT mass-distribution, preprogrammed automatic dialing mechanism and related processes |
| US4899365A (en) * | 1988-02-29 | 1990-02-06 | The Boeing Company | Apparatus and method for adaptive amplitude equalization |
| JPH02267756A (en) * | 1989-04-07 | 1990-11-01 | Nec Corp | Magneto-optical recording and reproducing system |
| US4995077A (en) * | 1989-10-30 | 1991-02-19 | Malinowski Igor P | Card-like device having a microprocessor and speaker for communicating with a telephone line |
| FR2705853B1 (en) * | 1993-05-28 | 1995-09-29 | Numerical Systems Communicatio | Device for automatic dialing of telephone numbers. |
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1995
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- 1996-09-25 PT PT96932653T patent/PT852867E/en unknown
- 1996-09-25 DK DK96932653T patent/DK0852867T3/en active
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- 1996-09-25 DE DE69613383T patent/DE69613383T2/en not_active Expired - Fee Related
- 1996-09-25 EP EP96932653A patent/EP0852867B1/en not_active Expired - Lifetime
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- 1996-09-25 WO PCT/FR1996/001500 patent/WO1997012467A1/en not_active Application Discontinuation
- 1996-09-25 AT AT96932653T patent/ATE202247T1/en not_active IP Right Cessation
- 1996-09-25 CA CA002231826A patent/CA2231826A1/en not_active Abandoned
- 1996-09-25 AU AU71353/96A patent/AU7135396A/en not_active Abandoned
- 1996-09-25 CN CN96198355A patent/CN1202289A/en active Pending
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2001
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| GR3036621T3 (en) | 2001-12-31 |
| ES2160838T3 (en) | 2001-11-16 |
| FR2739238A1 (en) | 1997-03-28 |
| DE69613383D1 (en) | 2001-07-19 |
| DK0852867T3 (en) | 2001-10-01 |
| ATE202247T1 (en) | 2001-06-15 |
| KR19990063748A (en) | 1999-07-26 |
| EP0852867B1 (en) | 2001-06-13 |
| CN1202289A (en) | 1998-12-16 |
| JPH11511628A (en) | 1999-10-05 |
| EP0852867A1 (en) | 1998-07-15 |
| DE69613383T2 (en) | 2002-02-14 |
| FR2739238B1 (en) | 2000-08-18 |
| BR9610649A (en) | 1999-02-17 |
| PT852867E (en) | 2001-11-30 |
| NO981334D0 (en) | 1998-03-24 |
| WO1997012467A1 (en) | 1997-04-03 |
| US5859913A (en) | 1999-01-12 |
| AU7135396A (en) | 1997-04-17 |
| NO981334L (en) | 1998-03-25 |
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| Date | Code | Title | Description |
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| FZDE | Discontinued |