FR2699031A1 - Automatic duplex or half-duplex momomode or multimode communication between two telephone units - Google Patents

Abstract

The communication method between two switched telephone units involves exchanging matching signal streams. A fast equipment sends out the matching signal in half duplex. The second equipment, on recognition and validation of the validation segment, emits a second signal in the recognised mode. The first equipment analyses the second signal, and if it recognises the signal it stays in the accepted mode for reception and sets up the communication. If the second transmission mode is slower, the second equipment does not recognise the first mode. In this situation, the roles of the equipment are reversed, and the validation procedure occurs w.r.t. the previous sequence but in the second mode of transmission.

Description

AUTOMATIC COMMUNICATION METHOD
DUPLEX OR SENI-DUPLEX OF TWO EQUIPMENTS THROUGH
A TELEPHONE LINE
The subject of the present invention is a method for setting duplex or semiduplex automatic communication (so-called duplex duplex) of a single-mode or multimode device and a single-mode or multimode device for modulations such as, for example,
V23, V27 ter and V29 through the general switched telephone network and on the peer-to-peer telephone circuits, such as two-wire leased circuits.

Since July 1, 1980, date of the first experimentation of the Directory service
Electronics in Saint Malo, the "Minitel" uses, in
France, a transmission rate of 1200 bits per second to receive the information of services consulted and a speed of 75 bits per second to transmit the input of the user. This mode of transmission, in full duplex ("full duplex") is based on the V23 modulation namely a speed of 1200/75 bits / s between the equipment "Minitel" and Access Point
VIdeotex ("PAVI"). The connection between the Minitel and the
PAVI relies on the Switched Telephone Network (PSTN). The link between the "PAVI" and the "Télétel" servers is based on the "TRANSPAC" network with transmission speeds of 19.2 Kbps or 48 Kbps.

In the early 90s, in order to improve the comfort and speed of consultation of "TELETEL" services, it was planned to increase the transmission speed first to 4800 bps and then to 9600 bps between
Access point and "Minitel". This new mode of transmission in half-duplex or half-duplex is based on the V27ter modulation for 4800 bps speed and on the V29 modulation for 9600 bps. The V27ter and V29 standards were selected for reasons of cost and performance. The 4800 bps and 9600 bps speeds can be used on both channels, with data circuit termination equipment (DCEs) or "modems" running in alternate directions.

 This new "Teletel" access service, called the "Fast Speed Teletel" (or TVR) access service, thus allows a useful communication rate multiplied by four in V27ter and by eight in V29 compared to the V23 access throughput. . I1 thus allows a fast transfer of pages requiring a large volume of information; it is the preferred channel for the operation of the future photographic "Minitel" and for applications such as file transfers, fax, audio-video, etc.

The consumer terminal (or "MINITEL") is not currently able to connect, indifferently and without specific intervention of the user, on access "Teletel" V23, access "Teletel" V27ter and on the next access
V27ter / V29 with connection times similar to the current V23.

 The establishment of the telephone link between the "MINITEL" and the PAVI is carried out mainly on the switched telephone network ("PSTN").

 The request for establishment of the link is constituted by the actions of taking the telephone line (or taking line) and numbering.

This request may be at the initiative
- the user (manual request)
- Minitel via the telephone directory
- a Minitel device such as the memory card reader or LECAM.

 The detection of this request for establishment of the connection by the remote equipment (call ringing on "PSTN" or positioning of a flag on leased line) authorizes it to perform the establishment of the link.

 After the establishment of the link, the communication or physical connection is effected by the exchange and recognition of signals between the modems of the two devices. The set-up validation allows the two devices to then transmit data and thus establish the logical connection such as setting the frame and packet levels of the communication protocol used for example V27ter and V29.

The call-up request (or "connection order" or "connection order") can be initiated
- the user by pressing a key such as the key "Connection-End" Minitel,
- Minitel via the telephone and telematic directory.

 - a Minitel device via a command sequence.

For a communication in V23 mode or
V27ter or V29 (V23 / V27ter / V29) it is possible to implement several keys "Connection-End" one for each mode. This manual solution is not ergonomic for a consumer user.

Another solution would be to rely on prior and systematic communication
V23 then, on reception of a particular sequence, passage in transmission V27ter or V29. This solution would be penalizing in connection time, and would not allow communication with existing equipment only V27ter, not having mode V23.

These solutions, manual or semi-automatic, would also have the disadvantage of prohibiting or making difficult any possibility of automatic restoration of communication (phonedonne application or audiovideotex) and the disadvantage of prohibiting any method of maintaining communication ( communication calls in V27ter or V29, and speed decrease of
V29 in V27ter).

The present invention relates to a method which does not have the aforementioned drawbacks and whose basic idea is to allow a reciprocal adaptation of the transmission modes of the calling equipment (generally the "MINITEL" or a "PAVI" or a terminal "PC" or "MACINTOSH" brand) and equipment called ("PAVI", "MINITEL", "PC" or "MACINTOSH" terminal). The terminal ("MINITEL", microcomputer, etc.) and the "PAVI" access point must be able to handle more than one modulation, and preferably, one and / or the other. regarding the calling equipment to handle either the two modulations V23 / V27ter or V27ter / V29 or the three modulations V23 / V27ter / V29 to allow
the physical connection in a transmission mode common to the two devices according to the fastest modulation preferably as presented in the summary table of the physical connection types (case of initial communication),
and / or the physical restoration of the communication in at least one mode, for example at least one of the three modes V23, V27ter and V29 (in the case of the voice-data application or audiovideotex).

For this purpose, the invention relates to a method of setting in duplex automatic communication of two equipment A and B through a telephone line characterized in that the two devices are arranged to communicate, after establishment of the telephone connection. according to at least one half-duplex transmission mode and in that the method uses at least one exchange of matching signal streams (eg long learning sequence) for communication with one another. in a duplex duplex transmission mode, each tuning signal stream starting with an unmodulated carrier signal (including an echo cancellation segment) of given nominal duration having a characteristic carrier frequency of said transmission mode. transmission requested, and also comprising at least one conditioning segment (for example segments 3, 4 and 5 of the V27ter or V29 long learning sequences) and in that each of the two devices is arranged to detect the frequency of said unmodulated carrier signal characteristic of said transmission mode used, and the method in which the two devices A and B are capable of carrying out an exchange of two transmission trains. matching signals according to the following steps
a) transmission by one of the equipment referred to as "first equipment for tuning" a first train of tuning signals according to a given mode of duplex transmission alternately.

 b) analysis by the other equipment, referred to as "second equipment for tuning" the frequency of the unmodulated carrier signal of said first tuning signal stream.

 c) in case of recognition by the second equipment of the frequency of the carrier signal of said given transmission mode, positioning of the second equipment in reception, according to said transmission mode, said conditioning segment.

 d) validation by the second equipment of the reception of said conditioning segment of the first train of tuning signals, and conditioning of the second equipment according to said given transmission mode, which allows it to transmit according to this mode.

 e) transmission by the second equipment of a second train of tuning signals according to the recognized transmission mode which corresponds to the given mode, which valid for the second equipment setting communication according to the given mode of transmission.

 f) analyzing by the first equipment the frequency of the unmodulated carrier signal of the second tuning signal stream.

 g) in case of recognition by the first equipment of the frequency of the carrier signal of the given transmission mode, maintaining the positioning of the first equipment in reception in said given transmission mode recognized and accepted by the second equipment.

 h) validation by the first equipment of the reception of said conditioning segment of the second train of tuning signals, and conditioning of the first equipment according to said given transmission mode.

 i) validation by the first equipment of the setting in communication according to said given mode of transmission.

 Said validation of the communication by the first equipment may comprise the transmission by it of a train of synchronization signals (for example short training sequence called "short train" mode V27ter or V29) not starting by an unmodulated carrier signal.

 It should be pointed out that the technique based on the exchange of tuning signal streams according to the method according to the invention can be used in a more general context such as that of a method for maintaining duplex communication at the same time. 'alternat relying on mechanisms of physical recovery of communication and / or fallback speed with change of the type of modulation such as V29 to V27ter modulation and / or V17 modulation (14.4 kbps) to V29.

The method according to the invention can allow the establishment of a communication between two equipment A and B having different speed transmission modes (case ne6), in which method the equipment A is arranged to communicate in a first mode transmission mode and a second half-duplex transmission mode slower than the first mode of transmission, and in that the equipment B is arranged to communicate according to said second transmission mode, but is not arranged for communicating according to the first mode of transmission and in that the equipment A and B are arranged to perform the exchange of two tuning trains according to the following steps
steps a) and b), in which the given mode of transmission is the first mode of transmission.

 j) in case of non-recognition by the equipment A of the frequency of the unmodulated carrier signal according to the first mode of transmission and the impossibility of the equipment B to be positioned according to said first transmission mode, non-validation by the equipment B of the reception of the first train of tuning signals.

 k) steps a) to i) in which the given mode of transmission is the second mode of transmission, in which the first equipment is the equipment B and the second equipment is the equipment A.

According to a variant, the invention relates to a method in which the second device is the equipment B and is arranged to communicate according to said first transmission mode (for example V27ter) as well as a third mode of transmission (for example
V29) in duplex faster than the first mode of transmission and, in that the first equipment, which is the equipment A, is arranged to communicate only according to said third mode of transmission.

 According to a preferred embodiment, each of the equipment A and B is capable of functioning either as first equipment or as second equipment. This makes it possible in particular to perform a matching for which the first equipment is either the calling equipment, that is to say which makes the line connection, (most favorable case) or the called equipment (for example so-called "delayed" connection).

 According to an advantageous embodiment, the unmodulated carrier signal is an echo cancellation segment used as a discriminant of the duplex transmission mode.

 A validation according to the mode of transmission adapted to the two devices is advantageously obtained by the fact that said validation of the setting in communication by the equipment validating the reception of the second train of signals of agreement, involves the emission of a train synchronization signals not starting with an unmodulated carrier signal.

In the case of a call-up request immediately following a line-seizure command (ie a request for the establishment of the telephone link (DLT)) (case of an anticipated connection), in other words, when the connection order is issued simultaneously or immediately after the line seizure order (see cases Nos. 1, 3, 6 and 7, which are exemplified hereinafter in the description), the method is characterized in that a call-up request is immediately following a request for establishment of the link by the equipment A and in that the equipment A and B are arranged to perform the following preliminary steps
0-0) request for establishment of the connection by the equipment A (order of taking line).

 1-0) detection by the equipment B of the request for establishment of the link and establishment of the link.

 2-O) transmission by the equipment B of a first signal of duration at least equal to a first given duration, of frequency equal to that of the response tone of an automatic response data equipment, having a frequency different from a half duplex modulation carrier signal frequency, followed by a second duration silence.

 3-O) detection by the equipment A of the presence of said frequency signal during at least said first given duration.

 4-O) measured by the equipment A of the second duration of said silence.

 5-O) if the second duration is greater than a given duration threshold, validation of the execution of steps a) to i) or steps a) to k), for which the first equipment is equipment A and second equipment is equipment B.

 The method may be characterized in that the equipment A and B are arranged to perform the communication in a non-half duplex transmission mode if, after the step 4-O), the equipment A measures a duration of silence below a given duration threshold.

 This method according to the invention thus also allows so-called downward compatibility "to a non-half-duplex (or" full-duplex ") operating mode, see case No. 1 exemplified in the remainder of the description).

The invention also allows so-called "delayed" communication. A first variant (case # 4 and # 8) of the method is for this purpose characterized in that a placing order is not immediately consecutive to an establishment of the connection by the equipment B, which is consecutive to a request for establishment of the connection by the equipment
A, in that the order of placing in communication occurs during a transmission sequence by equipment B of tuning signal trains according to the given mode of transmission, and in that said sequence of emission constitutes said step a), the first equipment being thus the equipment B and the second equipment, the equipment A.

 A second variant (Nabis and 9 cases) of this method is for this purpose characterized in that a placing in communication order is not immediately consecutive to establishment of the connection by the equipment B, which is consecutive to a request for access. establishment of the connection by the equipment A, and in that the order of communication occurs during a transmission sequence by the equipment B of tuning signal trains according to said second mode of communication. transmission less rapid than said first mode of transmission and in that it comprises the implementation of steps a) to i) according to the first transmission mode, during which the first equipment is the equipment B and the second equipment is equipment A.

A preferred variant (case No. 5bis) of the method is for this purpose characterized in that a placing in communication order is not immediately consecutive to establishment of the connection by the equipment B, which is consecutive to a request for establishment. the connection by the equipment A, in that the order of communication occurs during a transmission sequence by the equipment B of tuning signal trains according to said first mode of faster transmission than said second transmission mode, and in that the equipment A is arranged to communicate according to said second mode but not according to the first mode, and in that the equipment B is arranged to communicate both according to the first and the second mode. second mode, and in that the equipment A is arranged to analyze the carrier frequency according to the first mode, and in that it comprises the following steps
- Analysis by the equipment A of the carrier frequency of a said train of tuning signals,
in the case of recognition of said frequency according to the first transmission mode, validation of steps a) to i) according to the second transmission mode, during which the first equipment is equipment B and the first equipment is equipment A .

 The invention also relates to a method for establishing the communication in a fallback mode, for example the V27ter, slower than the V29 mode, but more robust than the latter.

According to one embodiment, corresponding to a setting in communication in a fallback mode (Nabis and 6 cases), the method is characterized in that for example in the case where the placing in communication order is immediately consecutive (case no. "(6) to an establishment of the equipment link B which is consecutive to a request for the establishment of the link A, or not immediately consecutive (case 4bis) the equipment A and B are arranged to perform before step a), the following preliminary steps
12-1) sending by the equipment A of a first train of tuning signals according to a first transmission mode.

 12-2) search by the equipment B for the presence of the frequency of the carrier signal.

 12-3) in case of non-recognition by the equipment B of the frequency of the carrier signal corresponding to the second mode of transmission, after a waiting time greater than a given duration threshold, validation of the execution of the steps a ) to i) according to the second mode of transmission, during which the first equipment is the equipment B and the second equipment is the equipment A.

 The invention also relates to a method for a voice-data switching providing a return protocol in duplex mode after a given time delay.

For this purpose, it is characterized in that said setting in communication is consecutive to a passage in speech mode (case 16 to 18) and in that it comprises the following preliminary steps
13-1) release of the duplex communication alternately successively to the logical levels of the communication protocol and then to the physical level (for example by falling carrier) while maintaining the link between the two devices.

 13-2) change to speech mode for a given delay time.

 13-3) detection of the end of the delay time.

 13-4) validation of the execution of steps a) to i) or steps a) to k).

In order to execute a communication order during the voice phase (cases 19 and 20), the method may be characterized in that the two devices A and B are arranged to detect the frequency of said carrier signal. unmodulated characteristic of each mode of transmission and in voice mode and that the equipment A and B are arranged to perform after the steps 13-1 and 13-2, the following steps 14-1) before the end of the duration of delay relative to the speech mode, initialization by one of the equipment of the setting in communication, by transmission of a placing order, for example a segment of given duration of unmodulated carrier frequency, intervening during the phase of speech.

14-2) validation of the execution of steps a) to i) of claim 1 or steps a) to k).

The invention also relates to equipment for carrying out the method according to one of the preceding claims and comprising a processing unit, a modem, a line interface and a control bus between the processing unit and the modem, the unit controller having a sequencer for sequentially programming said modem, characterized in that said sequencer is arranged to
- 15-1) programming the transmission by the modem of a tuning signal stream preceded by an unmodulated carrier signal,
- 15-2) schedule the modem to detect at least one unmodulated carrier frequency at the beginning of a received tuning train, and to position the modem in a half-duplex transmission mode corresponding to said carrier frequency, so as to allow the modem to receive the other signals of said received tuning train, and
- 15-3) to program a release of the physical duplex communication in alternate mode according to said mode of transmission once the modem has received and transmitted in a compliant way a said train of signals of agreement, allowing then performing an exchange of synchronization signal trains to validate a connection according to said transmission mode.

 The equipment may also be characterized in that the sequencer is arranged so that, when the modem is in reception mode, said detection of at least one unmodulated carrier frequency is carried out continuously.

According to an advantageous variant, the equipment is characterized in that said sequencer is arranged to validate said emission by the modem of a train of matching signals according to 15-1 when one of the following conditions is fulfilled.
- Receiving a compliant signal stream according to 15-2, - detection by the modem following a request for communication of a characteristic silence interval of said.

Other features and advantages of the invention will appear better on reading the following description, given by way of non-limiting example, in connection with the drawings which represent
FIGS. 1a and 1b, respectively, a block diagram of a "TELETEL" type transmission network illustrating different types of equipment and access points and a block diagram of a card fitted to a terminal and implementing a DCE component (technical data communication equipment) or "modem" programmable by bus and used to implement the invention,
FIGS. 2 to 20, cases 1 to 9 and 14, corresponding to different connection configurations, cases 10 to 13 corresponding to resumption-adaptation configurations and cases 15 to 20, to given voice switching configurations, the calling equipment being in the left-hand column, and the equipment called in the right-hand column, - FIGS. 21a to 21s for the R96-VFX modem, respectively, its programming in V29 (21a) mode and in V27ter (21b) mode. , the freezing of the coefficients of its filter (21c), its programming in short train mode (21d), its programming in transmission mode (21e) or reception (21f) of a short train or a long train, in V29 modulation or V27ter, its programming in frequency transmission (21g), successively for the programming and the emission of a frequency and for the stop of the emission of a frequency (21h), its programming in mode of detection of frequencies ( 21i), the programming coefficients of the filters FR1, FR2 and FR3 for the det ection of frequencies with the RAM address of the coefficients according to the filters (21j), and the integration constants d of the filters (21k), the detection of the 2100 Hz (211), the detection of the 1300 Hz (21m ), the detection of the 1800 Hz (21n), and the detection of the 1700 Hz (21O), the writing procedure in the RAM RAM of the modem (21p), the detection of a frequency with a filter (21q) ), the validation of segment 1 (unmodulated carrier) in data mode (2lr) and the validation of segments 3 and 4 (short train or long train) (21s).

FIGS. 22a to 22d, a transmission sequence respectively of a long train V29, a long train V27ter, a short train V29, and a short train V27ter, SI designating a unitary interval according to the standard ,
FIGS. 23a to 23d, a reception sequence respectively of a long train V29, a long train V27ter, a short train V29, and a short train V27ter,
FIGS. 24a to 24d, an end-of-transmission sequence respectively in long-wave mode V29 (24a), in long-wave mode V27ter (24b), a data transmission and end-of-transmission sequence in train mode. short V29, as well as in V29 long train mode in case of recovery (24c), and a transmission sequence of data and end of the emission in V27ter short train mode, and in V27ter long train mode in case of recovery (24d),
FIGS. 25a to 25f, an end of reception sequence respectively after a long train V29 (25a), after a long train V27ter (25b), a sequence of reception of the flags and data and the end of reception in short train mode V29 (25c), in the V27ter (25d) short train mode, in the V29 (25e) long train mode and in the V27ter (25f) long train mode,
FIG. 26a, an equipment communication automaton (calling mode and called mode) being understood that a particular piece of equipment can implement the two modes, or only one of the modes, and FIG. 26b the beginning of FIG. connection controller (line socket) in both modes.

FIGS. 27a to 27g, the calling-up connection automaton and implementing elementary sequences of FIGS. 22a to 25f,
FIGS. 28a to 28e, the called mode connection automaton of FIG. 26 and implementing elementary sequences of FIGS. 23 to 25,
FIGS. 29a to 29c, a data switching automaton given and implementing elementary sequences of FIGS. 22a to 25f,
FIGS. 30a to 30d, an adaptive communication and revision-adaptive autmate
V29 (30a and 30b) and V27ter modulation (30c and 30d) and implementing elementary sequences of Figures 22a to 25f.

In FIG. 1A, videotex 14, audiotex (voice) 15, videotex and photographic servers 16 connected to the TRANSPAC network, are accessible to users 1 to 6 by the switched telephone network through videotex access points (PAVIs), V23 (asynchronous 7 bits plus parity bit for example numbering 3614 or 3615 in France) or in
V27ter and / or V29 (8-bit synchronous). A terminal (V23) for example microcomputer V23 1 or Minitel V23, 2 can only access a PAVI V23. On the other hand, a multimode terminal, for example Minitel 3 (V23 / V27ter) or 4 (V23 / V27ter / V29), microcomputer 5 (V23 / V27ter / V29) or Access Service Microcomputer 6 V23 / V27ter / V29, may have access to all PAVIs. A single mode terminal
V27ter or V29, for example a microcomputer 5, can have access to a corresponding PAVI V27ter or V29.

 The terminal 6 allows in particular a file transfer application (STUTEL) and secure (LECAM: Memory Card Reader 1200 or 4800/9600 bps). The invention therefore proposes a method for automating connection procedures for single-mode or multimode operation in at least two modes.

The method according to the invention, while having the same behavior as V23 connection "MINITEL""fullduplex" allows and optimizes the connection of "Minitel" (backward compatibility) on TVR accesses (V27ter Fast Speed Terminal and / or
V29) and on accesses V23, without any particular action of the user (key Connection-End), by automatic distinction of the speed of transmission. The distinction between two modulations or three modulations is based on one or the other of two discriminants, one to differentiate the fast speed from the normal speed (V23), the other to separate the two modulations selected in fast speed (V27ter / V29).

1) Physical establishment of communication
During the automatic response operation, the echo suppressors are neutralized by the 2100 Hz response tone (see recommendation
V25 of the CCITT). The presence of this tone is justified for transmissions of the full duplex ("fuli-duplex") or partial ("semi-fulî-dupîex'1) type, for example in V23. alternating ("half-duplex") as in V27ter and V29, the echo protection devices are restarted by a signal stop (silence) equal to or greater than 100 ms. "full-duplex" (V23), the neutralization of these devices is maintained by the reappearance of the signal before the expiration of a period of 75 ms + or - 20 ms These provisions provided by the standards have no reason to only in the case of a satellite link.

This difference in the duration of silence is used, according to the invention, to differentiate the V23 mode, V27ter modes and V29 (first discriminant). The specified values are as follows: silence of 75 ms + or - 20 ms for V23 mode, - silence of 150 ms + or - 20 ms for fast speed mode V27ter / V29.

This first discriminant needs to be implemented only for equipment likely to access networks according to the different types of duplex link.

 It should be noted in particular that the equipment according to the invention can be provided for example only to operate in V27ter and / or V29.

The first discriminant can be implemented alone for equipment intended to operate in
V23 and in V27ter mode, or in V23 mode and in
V29, in the case of so-called normal connection anticipated.

The second discriminant, which makes it possible to identify two half-duplex operating modes according to two different rates, for example, between the V27ter and the V29, is, according to the invention, the frequency of the signal of the carrier which is 1800 Hz in V27ter and 1700 Hz in V29.

According to the invention, a signal at the frequency of the unmodulated carrier is sent at the beginning of the long learning sequence (long train). The equipment receiving this signal detects its frequency and can automatically position its modem in the required mode (matching) or find that it can not operate in the modulation with this carrier frequency. A long learning sequence thus fulfills, according to the invention, the function of matching the two devices on the same modulation.

According to a preferred embodiment, discriminating segments used for echo suppression in the satellite links are used.

Indeed, these segments implement a transmission of the unmodulated carrier for a period of 185 to 200 ms followed by a silence of 20 ms at the beginning of long learning sequence (long train); this issue corresponds to segments 1 and 2 as described in CCITT recommendation V27ter and V29. In the prior art, the presence of these segments in advance of the training sequences corresponds to the "speaking" mechanism on the satellite links; indeed, the echo suppressor devices use threshold detection systems that have a significant response time; it is to guard against this response time that the "speaking" mechanism, based on segments 1 and 2, is used in a satellite link.

The invention takes advantage of the recognition that the duration of the segment 1 (185 to 200 ms) is compatible with the programming time of a modem, and in particular of its reception filter, which allows the intended application .

The speaking mechanism available by the presence of the segments 1 and 2, is thus saddles the invention deviated from its primary function to be used as V27ter / V29 discriminant. Modulations
V27ter and V29 use different carriers: the carrier frequency in V27ter is 1800 Hz and that in
V29 is 1700 Hz. Because of its ability to reliably detect tones by digital filtering, the DCE component (or modem) makes it possible, during the initial connection, as will be described later, to distinguish these two frequencies when the long learning sequences are transmitted with the segments 1 and 2. This therefore makes it possible to program the modem in the mode chosen (in agreement), to receive correctly the corresponding long learning sequence. According to a preferred mode, a sequence long learning can only be validly received if its carrier frequency (segment 1) has been recognized by the receiving modem. If the carrier frequency is not recognized, the training sequence is detected as non-compliant. The modem of a device is programmed to recognize the carrier frequency of the modulations that it can receive and transmit (for example a device that can not operate in V29 does not necessarily recognize the frequency 1700 Hz, which allows an effective discrimination of various cases as will be described later). According to the invention, the segments 1 and 2 are, however, not used in the short training sequences (synchronization) transmitted to each modem reversal to not slow down the useful rate of communication.

It will be recalled that the exchange of data is done in packets. A packet transmitted in one direction is preceded by a short learning sequence (synchronization). After receiving the packet, the two modems are "turned over", so as to exchange their transmission-reception functions, and a packet is transmitted in the other direction, preceded by a short training sequence, and so on.

2) Physical recovery during communication
The mechanism based on the presence of segments 1 and 2 allows to implement the voice-data switching process. This alternation of use of the phone line in voice mode and given mode is currently available on the models M10-M12 (V23 modulation) of "Minitel" equipped with an integrated telephone.

For the V27ter and V29 modulations, when returning to connected mode (or data mode), the use of the same process with the transmission of long learning sequences (and the presence of segments 1 and 2) makes it possible to reliably manage the recovery. physical communication in the appropriate modulation V27ter or
V29 with test in the fastest modulation. The application software must in this case manage a context for the V23 or V27ter / V29 telematic communication recovery mode in the absence of the discriminant normal speed / fast speed (duration of silence). Moreover, in fast speed mode, unlike recovery and fallback processes, the communication software must completely restore the different higher levels (connection frame and call packet).

For the record, recall that according to the prior art, in V23 mode, the "reconnection" is of simplified type by detection of 600 ms at least 1300 Hz without seeking the frequency 2100 Hz; the error correction procedure is activated by the user.

The automatic processes of physically establishing the call and restoring during a call make it possible, according to a preferred embodiment, to establish automatically the connection in the three modulations and the returns in connected mode for the voice application. given.

The voice-data application known per se in V23 is renewed in a fast speed by the introduction of the V27ter / V29 automatic connection process allowing programmable alternations of the speech mode to the given mode, for example for an audiotex or audiovideotex service at 9600 bps.

3) Physical recovery during communication
The physical recovery process is implemented in particular during variations of the template of the line or during disturbances generating erroneous short sequences. It makes it possible to perform a new matching of the equipment according to the same modulation allowing resynchronization of the modems at both ends according to the new characteristics of the line.

Due to the possibility of dial tone detection of the modem component during communication, it is possible to distinguish the unexpected presence of a carrier in the original transmission modulation.
V27ter or V29. This mechanism of resumption of transmission is possible by the presence of segments 1 and 2 of the long learning sequence indicating the beginning of the recovery process. The "speaking" mechanism is here also used as an indication signal of a physical recovery, during communication, for example at the initiative of the remote equipment.

The recovery mechanism can be based on the possibility for the receiving equipment, in case of reception of one or more erroneous synchronization short sequences (alternat), to perform a new physical matching. In fact, during communication, the desynchronism of the two modems (non-convergence of the equalizers) can be generated by variations of the template of the line or during disturbances on the telephone network. Contrary to the case of the passage in voice mode, and in data mode, this phase of connection is carried out only at the physical level without loss of connection of the higher levels namely the level field and the level packet, and without modifying the parameters of these levels This is made possible, as will be described later, by the fact that the time it takes to set up a new connection at the physical level, that is to say the time required for exchange of long learning sequences, remains short enough for the controller, known per se, which manages the connection at the frame level and at the packet level, remains in a data waiting mode. In other words, for the automaton (frame / packet) everything happens, during a recovery phase, as if the other equipment was slow to send data.

It should be emphasized that the exclusive use of short learning sequences (without segments 1 and 2) to obtain a useful throughput for the intended applications is based on the assumption of a stationary transmission line (no learning sequence long permanently) and short distance ("Minitel" - "PAVI").

4) Falling V29 communication speed in
V27ter
Due to the possibility of tone detection during communication and more particularly during resumption of communication, it is possible to distinguish the presence of a carrier in the V29 transmission (V27ter). This fallback mechanism is possible by the presence and detection by the receiving equipment of segments 1 and 2 of the long learning sequence indicating the beginning of the fallback process and the modulation used.

The fallback mechanism is based on the possibility that the receiving equipment, in the event of receiving an erroneous long learning sequence, is present during the resumption process in modulation.
V29, to resynchronize at the physical level of modems in V27ter modulation. If the particularly difficult reception conditions do not make it possible to successfully resume communication in V29, it is then possible to resynchronize the modems V27ter, given the better robustness of this modulation vis-à-vis disturbances of the line.

As in the case of physical recovery, the mechanisms of resumption of communication and retraction of speed do not disturb the higher levels (frame and packet), although there is change of modulation.

These last two processes (recovery and fallback) offer the possibility of maintaining communication, specifically and physically, even in difficult reception conditions due to disturbances affecting the quality of the transmission medium. They allow, in terms of application, to avoid prematurely breaking the transmission, which is very important, especially in the case of file transmission; this optimum self-adaptation of the V27ter / V29 transmission is likely to allow, whatever the physical medium, not only comfortable interactive communications, but also fast and reliable information transfers.

The invention will now be described in more detail with examples corresponding to the transmission modes V23, V27ter and V29.

Reference will be made, as prior art, to the following documents - CCITT Recommendation V25 (in particular last paragraph of Chapter 5, page 129), the connection procedure used in the "Minitel".

- CCITT Recommendation V27ter (in particular the long and short learning sequences defined in Table 3 on page 202), - CCITT Recommendation V29 (in particular the long learning sequence defined in Table 5 on page 221), - Annex F of the CCITT Recommendation T104 to standardize the short V29 training sequence with segments 1 and 2, required for the fast speed function of 9600 bps "Minitel", - CCITT recommendation X32 (in particular LAPX frame synchronization and packet X25.3, implemented in particular on EBS network equipment
TRANSPAC, - CCITT recommendation T71 (special features of LAPX), and TELETEL equiments Speed Fast (V27ter / V29) - recommendations T104 (pr ETS 300221) and T105 (pr ETS 300223) of the CCITT, - STUPAV (technical specifications videotex access point users) (version 1991) from FRANCE
TELECOM, - STUM (Technical Specifications of Users of "MINITEL" (versions 2VRP, M1B, M2, and M12) of FRANCE
TELECOM.

In order to improve the comfort and speed of consultation of "Teletel" services from "Minitel" type professional, it is planned to increase the transmission speed to 4800 Bits / s then to 4800/9600 Bits / s between Access Point "Teletel" and "Minitel".

V27ter modems (4800 bits / s), V29 (9600 bits / s) of facsimile type 3 are known (ROCKWELL R96 VFX).

The transmission rate is 9600 or 4800 Bits per second on both channels, with the modem running in alternate mode.

The actual bit rate of the "PAVI" - "Minitel" link is optimized by the use of short training sequences at each reversal of the modems, the characteristics "short and stationary line" of this link allowing the use of this mode. The V27ter standard has both types of learning sequences (long and short) but the standard
V29 initially has only the long learning sequence. For this purpose, based on the R96VFX component, the Rockwell company developed, in collaboration with the Applicant, the V29 short learning sequence, which is integrated in Appendix F of the CCITT Recommendation T104.

The communication protocol between "PAVI" and "Minitel" fast speed, establishment, management and release, is in accordance with recommendations X25, X32 and T71 of CCITT, STUR TRANSPAC and recommendations T104 and T105 of the CCITT and the services of basis of the draft ETSI prETS 300 221 and
ETS 300 223.

Physical connection procedure (line level)
The physical connection process of the equipment according to the invention allows the automatic adaptation of the transmission speed to that of the called equipment, while presenting the same process as in connection
V23 and respecting the recommendations V25 and V100 of the
CCITT.

The main objective is to specify the physical connection processes of the "Minitel" V23 / V27ter, the "Minitel" V23 / V27ter / V29 and the "PAVI" V27ter and
V29 / V27ter, taking into account the following constraints - optimize connection times with "Minitel" evolved in terms of Speed V23 / V27ter / V29, "Minitel" 2 VRP (Fast Photographic Speed)
V23 / V27ter and the "Minitel" 2 VR (Fast Speed)
V23 / V27ter / V29, and / or - have a behavior compatible with V29 / V27ter "PAVI" accesses at 9600/4800 bits / s with respect to terminals calling at 4800 bps or 9600 bps (backward compatibility), and / or - allow the connection of modem cards and boxes
V27ter currently existing (eg "EBS
Transpac "), and / or - automatically distinguish the connection of the" Minitel "on a" PAVI "V23 from that on a" PAVI "Fast Speed
V29 / V27ter without special action of the user.

The basic principles are related to the possibilities of V27ter / V29 modems currently on the market (eg the R96EFX / VFX) which, thanks to their internal signal processor, also reliably provide selective digital filtering functions.

The originality of the connection principle is therefore based on the preliminary analysis of the pure frequencies or tones present on the telephone link. Indeed, before any connection attempt, a detection of the tones makes it possible to discriminate the carrier frequencies of the modulations V27ter, V29 and the rest frequency of the modulation V23 (respectively 1800 Hz, 1700 Hz and 1300 Hz), even the telephone signaling ( 440 Hz clocked). The unmodulated frequencies in V27ter and V29 with a duration of 187.5 ms for the R96VFX correspond to the first segment of the long learning sequence. (cf recommendation
V27ter and V29 for the meaning of the segments of the short and long learning sequences).

Similarly, the originality of the principle of readaptation is based on the analysis during communication of the carrier frequencies of the modulations
V27ter, V29 allowing a resumption of the physical level (synchronization of the modems clocks) without disturbing the higher levels, either during variations of the line template or during disturbances, and more generally of any cause generating erroneous short training sequences , on the order of one of the equipments.

It should be noted that the full recovery mechanism, leading to a change and in particular a modulation fallback (V29 -> V27ter), maintains the parameters of the higher levels (for example the packet level anticipation window), leading to a slight decrease of interactivity.

Based on this principle of detection of tones by digital filtering, this operation allows the "Minitel" V23 / V27ter / V29 to adapt, quickly and reliably, their transmission speed with respect to a remote device (V23, V27ter, V29) and with respect to the used line (template, disturbances, etc ...).

The characteristic tones detected by the modem in the connection phase are - 440 Hz to detect the telephone signaling, - 1300 Hz to enable the management of the V23 connection - 1700 Hz to detect the unmodulated carrier V29, - 1800 Hz to detect the non-carrier V27ter modulated, - 2100 Hz to handle the CCITT recommendation V25.

The characteristic tones detected in the communication phase for eventual physical recoveries are - 1700 Hz to detect the unmodulated carrier V29 (recovery in V29), - 1800 Hz to detect the unmodulated carrier V27ter (recovery in V27ter).

We distinguish two cases: the operating principle for the called equipment and that for the calling equipment. It is the modem of the called equipment which, following an incoming call, responds in a known manner by the 2100 Hz tone (see recommendation V25). In general, the access point "PAVI" is the called equipment, the "Minitel" is the calling equipment. However, the establishment of the physical connection can be obtained, as will be seen later, on one or the other equipment, depending on the case, after exchange without fault of long train tuning: the first equipment sends a long tuning train; if the second equipment receives it correctly, it in turn transmits a long tuning train; if the first equipment receives it correctly, communication is established at the physical level, which results in the first equipment transmitting a short synchronization train, followed by data, or signals to establish the frame-level communication then back to the packet level, in a manner known per se.

The hardware architecture of the V27ter modem accesses of "PAVI" Fast Speed ("PAVI" VR) (usually called equipment) is based on the R96EFX
Rockwell. That of access V29 / V27ter "PAVI" VR second generation is based on possibilities at least equal to the R96VFX box (digital filtering capacity, short train V29 ...).

The access of the "PAVI" VR (fast speed) being only called to 9600/4800 bits / s, only the detections of the frequencies carrying modulations
V27ter (1800 Hz) and V29 (1700 Hz) are required at this level.

The synoptic of a MINITEL card Fast speed
V23 / V27ter / V29 according to the invention is given in FIG. 1B. It includes an INTEL 80C154-1 microcontroller MC connected via a BUS bus link to a 32k SRAM "NEC" 43256 SRAM. bytes associated with a backup stack
P, to a programmable read-only memory EPROM of the company "INTEL" 27C512 of 64 k. bytes and an MDM1 modem from the company "ROCKWELL" R96VFX (V27ter / V29). The MC microcontroller is connected to an MDM2 "HERMES" V23 (ALCATEL) modem via a serial TTL-type LS link. The outputs of the MDM1 and MDM2 modems are applied to the inputs of a DX duplexer for connection to an LT telephone line. It will be understood that such a MINITEL card can operate in V27ter / V29 only by removing the modem MDM2.A card
Minitel operating only in V27ter can be realized using as modem MDM1, a modem
R96EFX.

Connection phase detection - In reception mode of the long learning sequence V29 or V27ter is associated a detection filter of 1700 Hz and 1800 Hz. The reception mode is activated after the emission of 3.3 seconds of 2100 Hz followed by a silence of 150 ms plus or minus 20 ms.

- On reception of segment 1 of the long learning sequence (identification for at least 100 ms of the unmodulated 1700 Hz frequency), the "PAVI" programs the modem in reception mode V29 for reception of the long learning sequence complete (packaging segment). The "PAVI" then transmits for sending the corresponding long learning sequence (segments 1 to 5).

The physical connection is established in V29 modulation.

- On reception of segment 1 of the long learning sequence (detection of at least 100 ms of the frequency 1800 Hz unmodulated), the "PAVI" programs the modem in reception mode V27ter for the reception of the training sequence long full. The "PAVI" then transmits for sending the corresponding long learning sequence. The physical connection is established in V27ter modulation.

Two cases are to be considered depending on whether the equipment includes a V29 / V27ter modem or only V27ter.

a) Case of a V29 / V27ter modem (such as R96VFX) - Without known frequency reception, after a delay of 2 seconds after the end of the 2100Hz tone emission, the "PAVI" V29 / V27ter defaults to the next processing. sending a long learning sequence V29,. without response from the remote device after 2 seconds, renewal of the sending of a long learning sequence V29, no response from the remote device after 2 seconds, last connection attempt in V29 mode by a new sending of a long learning sequence V29,
without response from the remote device, attempt to connect in V27ter mode by sending a long learning sequence V27ter,
without response from the remote device after 2 seconds, sending a short learning sequence
V27ter,. then complete renewal of the mechanism described in the two previous paragraphs (long train + short train) until the expiry of the connection waiting time delay (usually 40 seconds) or on the response of the remote equipment.

b) Case of a V27ter modem (such as R96EFX) - Without known frequency reception, after a delay of 2 seconds after the end of the 2100Hz tone emission, the "PAVI" only V27ter performs the processing next - sending a long learning sequence V27ter, - no response from the remote device after 2.

seconds, sending a short learning sequence
V27ter,. then complete renewal of the mechanism described in the two previous paragraphs (long train + short train) until the expiry of the disconnection timer or on the response of the remote equipment.

Principle of detection in the communication phase (recovery process)
Two processes are to be considered, depending on the influence of online disturbances and real-time variations "of the transmission line mask * mechanism of recovery in the original modulation in
V29 (case ne11) or V27ter (case ne10), * fallback mechanism in V27ter modulation with V29 origin modulation (cases No. 12 and 12bis).

The hardware architecture of "Minitel 2" Speed
Fast Photographic (M2 VRP) and "Minitel" 2 fast speed VR (in general calling equipment) is based on Rockwell's R96 VFX modem box and on the Hermes case or its equivalent case
ST7514 from SGS-Thomson. In fact, these "Minitel" can connect indifferently to doors "Teletel" V23 and V27ter. Only 2100Hz, 1300Hz, and 1800 tones
Hz are then detected during the connection phase. In addition, the 1800 Hz tone is detected in the communication phase to ensure an erroneous short-circuit readaptation process.

It is possible to discriminate between modes V23 and
V27ter only with the first discriminant (nominal duration of the silence of 75 or 150 ms), and thus not to detect the frequency 1800 Hz. The reception of a long learning sequence V27ter is done on the segments 3 to 5 only , the modem having been set in this mode after detecting a silence of 150 ms.

The Minitel Speed V23 / V27ter / V29 must be able to connect indifferently to doors "Teletel" V23, V27ter and V29 / V27ter. As a result, the 2100 Hz, 1300 Hz, 1700 Hz and 1800 Hz tones are detected during the connection phase. In addition, the 1700 Hz and 1800 Hz tones are detected in the communication phase to ensure the physical recovery-adaptation process. The 440 Hz tone can be searched continuously to monitor the telephone signaling.

At the touch of the connection / end key, the "Minitel" is connected to a line connection and is able to detect the frequencies 2100 Hz, 1800 Hz, 1700 Hz and 1300 Hz, the frequency 440 Hz is sought if energy is present on the line, without presence of the previous frequencies. These frequencies are validated if the duration of the signal is at least equal to 300 ms for the 2100 HZ, 80 ms for the 1300 Hz, 100 ms for the 1700 Hz and 100 ms for the 1800 Hz.

The "Minitel" 2 Fast Photographic Speed switches to V23 modulation if - 300 ms of 2100 Hz are detected followed by 75 ms (+ or - 20 ms) of silence then of 80 ms of 1300 Hz, - the frequency of 2100 Hz n ' is not detected, but the frequency of 1300 Hz is detected for 1.7 s (or 1.8 s from the M2).

This behavior meets the requirements of the STUM recommendations for the entire management and connection part in V23 modulation.

The "Minitel" Fast Photographic Speed switches to V29 modulation and emits its long learning sequence if - at the reception of the frequency 2100 Hz, the following silence is 150 ms (+/- 20 ms) knowing that the modulation the fastest of the "Minitel" is the V29, - segment 1 of the long learning sequence (187.5 ms of 1700 Hz validated for 100 ms) is detected by the digital filter; the "Minitel" programs the modem in reception mode V29 to receive the complete long learning sequence. The physical connection is established by programming the modem V29 modulation in the mode of short training sequences, after the transmission of the long learning sequence V29, - detection of three short sequences V29 consecutively erroneous (recovery process).

The "Minitel" evolved in terms of Fast Speed switches to V27ter mode and emits a long learning sequence if - on receiving the frequency 2100 Hz, the following silence is 150 ms (+/- 20 ms) knowing that the fastest modulation of the "Minitel" is the V27ter, - the segment 1 of the long learning sequence (187.5 ms of 1800 Hz valid for 100 ms) is detected by the digital filter, the "Minitel" program the modem in V27ter receive mode for receiving the complete long learning sequence. The physical connection is established by programming the modem V27ter modulation in the mode of short training sequences, after the transmission of the long learning sequence V27ter.

- On receiving the frequency 2100 Hz, the following silence is 150 ms (+/- 20 ms) knowing that the fastest modulation of the "Minitel" is the V29. The "Minitel" then transmits the long learning sequence
V29. If, at the expiry of a delay of 10 seconds, the correspondent (generally a "PAVI" access point) has not transmitted a known frequency, the "Minitel" programs the modem in reception mode V27ter in order to detect the presence of an incomplete V27ter training sequence (absence of segments 1 and 2, as is the case for EBS). To do this, it suffices to delete the logical detection condition of the segments 1 and 2 in the sequencing. The validation of the reception of a conformal long train is then carried out in a conventional manner on segments 3 to 5.A of the V27ter long train incomplete, the "Minitel" transmits in response the complete long learning sequence V27ter (there is no problem in transmitting the segments 1 and 2) and the communication is established in V27ter modulation, in the short learning sequence mode, - when receiving the 2100 Hz frequency, the following silence is 150 ms (+/- 20 ms) and the fastest modulation of the "Minitel" is the V29, the Minitel emet then the long learning sequence V29. If the "Minitel" detects the presence of the unmodulated frequency (or segment 1) of the V27ter (187.5 ms of 1700 Hz validated for 100 ms), then it programs the modem for the reception of the long learning sequence
V27ter. In response to the long learning sequence
V27ter complete, the "Minitel" emits the complete V27ter long learning sequence. Communication is established in V27ter modulation, in the mode of short learning sequences.

consecutive detection of, for example, three errored V27ter short sequences or for example three erroneous V29 short sequences followed by one or two erroneous long V29 sequences (recovery process).

According to the invention, a long learning sequence (segments 3 to 5) is preceded by the transmission of, for example, 180 to 200 ms of unmodulated carrier (segment 1) followed by 20 ms of silence (segment 2). The transmission of the long learning sequence is conditioned for the calling equipment
For V29 modulation - either by recognition of the 2100 Hz frequency for 300 ms followed by a silence greater than 150 ms, - by the recognition of the 1700 Hz frequency for 100 ms followed by the recognition of the training sequence long V29 issued by the modem of the called equipment, - either by the recognition of the frequency 1800 Hz for 100 ms followed by the recognition or not of the training sequence V27ter emitted by the modem of the called equipment, - either by the consecutive detection of three erroneous short V29 learning sequences (recovery process).

For V27ter modulation - either by recognition of the 1800 Hz frequency for 100 ms followed by the recognition of the V27ter long learning sequence transmitted by the modem of the called equipment, - or by the recognition of the 1700 Hz frequency during 100 ms followed by the non-recognition of the long learning sequence V29, modulation not managed by the calling equipment, or by the only recognition of the long learning sequence V27ter received without the presence of the segments 1 and 2 (case of EBS), - either by the consecutive detection of three erroneous V27ter short training sequences (recovery process), - or by the consecutive detection of three erroneous V29 short training sequences followed by a training sequence long erroneous V29 (recovery process).

For called equipment, the transmission of a long learning sequence (matching) is also always preceded by the transmission of 180 to 200 ms of unmodulated carrier (segment 1) followed by 20 ms of silence ( segment 2> The transmission of the long learning sequence is conditioned
For V29 modulation - either by 100 ms recognition of 1700 carrier
Hz followed by the detection of the long learning sequence V29, - either by the expiry of the delay of 2 seconds of waiting of tone, - or by the consecutive detection of three erroneous V29 short learning sequences (process of reprise).

for V27ter modulation - either by the recognition of 100 ms of carrier 1800
Hz followed by the detection of the long learning sequence V27ter, - either by the expiry of the delay of 2 seconds of waiting of tone, - or by the recognition of a long sequence
Learning V27ter without presence of segments 1 and 2 (case of EBS), - either by the consecutive detection of three erroneous V27ter short learning sequences (recovery process), - or by the consecutive detection of at least one, and for example three short learning sequences
V29 erroneous followed by one or two erroneous long V29 learning sequences (recovery process).

In order to pass into a short learning sequence (synchronization), which characterizes the connection at the physical level, the following two conditions must be met - having recognized the long learning sequence emitted by the remote modem, - having issued its own learning sequence long.

The modems of the two devices are synchronized and the exchanges then take place in the mode of the short training sequences.

During communication, if the modems are out of synchronization, the connection recovery process provides a return to the long learning sequences either in the same modulation or V27ter in case of desynchronization and failure of recovery in the V29 modulation (process fallback).

Diagrams of different types of connection
We have identified 6 configurations (cf case N 3 to 9) of fast speed connection given the diversity of equipment "Minitel" V23, V23 / V27ter,
V23 / V27ter / V29 and "PAVI" V23, V27ter, V29 / V27ter. In addition, we studied the configuration (cf Figure N "14) of connection of" Minitel "on the inputs
Synchronized Tunables of TRANSPAC (EBS).

Each case is the subject of a diagram to visualize the sequence of the physical connection process and to evaluate the connection time.

An early connection is defined as any semiautomatic or manual connection where the calling device recognizes 300 ms of 2100 Hz. The connection order (for example pressing the end-connection key or sending a sequence according to the protocol " Minitel ") arrives before the last 300 milliseconds of the 2100 Hz tone to the line management software.

Delayed connection is any connection (a priori manual) where the calling device can not recognize 300 ms of 2100 Hz. The connection order reaches the line management software in the last 300 milliseconds of tone 2100 Hz or later.

We call equipment V23 / V27ter or equipment
V23 / V27ter / V29 any material called, a "PAVI"
VR is a "Minitel" used in so-called "front-end" mode (micro-pavi), or any device likely to be called and to meet the specifications of this document. We can specify that the behavior of the calling equipment can be applied to the terminal "Minitel" as well as to the "PAVI".

Segments 1-5 of a learning sequence
V27ter or V29 are as follows (according to recommendations
CCITT)
Segment 1: unmodulated carrier
Segment 2: no energy transmitted
Segment 3: Continuous Phase Inversions of 180
Segment 4: equalizer conditioning sequence: 2 phases 0 and 1800
Segment 5: Continuous emission of scrambled "1".

SI = unit interval of the dibit; the durations of segments 3 to 5 are expressed in unitary intervals.

On the diagrams, the abbreviations represent respectively
TL: long learning sequence or long train (establishing agreement)
TC: short learning sequence or short train (synchronization)
TLV27: V27ter Long Learning Sequence or V27ter Long Train
TLV29: long learning sequence V29 or long train V29
TCV27: V27ter short training sequence or V27ter short train
TCV29: V29 short training sequence or V29 short train
TLV27: segment 1: 185 to 200 ms of unmodulated carrier; segment 2: 20 to 25 ms without transmitted energy; segment 3: 50 SI (unit intervals) segment 4: 1074 SI; Segment 5: 8SI
TC V27: no segments 1 and 2; segment 3: 14 SI segment 4: 58 SI; segment 5: 8 SI
TL V29: segment 1: 185 to 200 ms; segment 2: 20 ms; segment 3: 128 SI; Segment 4: 384 SI; segment 5 48 SI
TC V29: no segments 1 and 2; segment 3: 100 SI; segment 4: 62 SI; segment 5: 18 SI.

The nominal duration of the learning sequences is - TL V27 = 915 ms (including segments 1 and 2), - TL V29 = 441 ms (including segments 1 and 2), - TC V27 = 50 ms (without segments 1 and 2), - TC V29 = 75 ms (without segments 1 and 2).

The physical connection is established after the exchange between the two ends, long learning sequences, when passing in short learning sequences to establish the connections of the frame levels
LAPX and X25.3 package.

The table summarizing the types of physical connection and recovery (cases 1 to 14) is given below
Summary of physical connection typesv qq se

<tb><SEP> Caller <SEP> called <SEP> mode <SEP> case <SEP> N <SEP>
<tb><SEP> V23 <SEP> V23 <SEP> Anticipated <SEP>
<tb><SEP> V23 <SEP> V23 <SEP> Delayed <SEP> 2
<tb><SEP> V23
<tb><SEP> V27ter / V23 <SEP> V27ter <SEP> Anticipated <SEP> 3
<tb><SEP> V29 / V27ter <SEP> 3
<tb><SEP> V23 <SEP> 2
<tb><SEP> V27ter / V23 <SEP> V27ter <SEP> Delayed <SEP> 4
<tb><SEP> V29 / <SEP> V27ter <SEP> 5,5a <SEP>
<tb><SEP> V23
<tb> V29 / V27ter / V23 <SEP> V27ter <SEP> Anticipated <SEP> 6
<tb><SEP> V29 / V27ter <SEP> 7
<tb><SEP> V23 <SEP> 2
<tb> V29 / V27ter / V23 <SEP> V27ter <SEP> Delayed
<tb><SEP> V29 / V27ter
<tb><SEP> V27ter / V23 <SEP> V27ter <SEP> Recovery <SEP> lo <SEP>
<tb><SEP> V27ter <SEP> -to <SEP>
<tb> V29 / V27ter / <SEP> V23 <SEP> Recovery <SEP> Recovery
<tb><SEP> V29 / V27ter
<tb> V29 / V27ter / V23 <SEP> V29 / V27ter <SEP> recovery <SEP> with
<tb><SEP> change <SEP> of <SEP> mode
<tb> V29 / V27ter / V23 <SEP> V29 / V27ter <SEP> Failure <SEP> 13 <SEP>
<tb> V29 / V27ter / <SEP> V23
<tb><SEP> EBS <SEP> Transpac <SEP> Early <SEP> lX <SEP>
<tb><SEP> V27ter / V23
<Tb>
The estimations of the connection times as a function of the connection modulations, calling devices (for example "Minitel") and called devices, are the following (see summary table V23 modulation connection (including the transmission of the connection sequence 13, 53)
Case N "1 - early connection to 1200/75 bps of equipment (" Minitel ") V23 / V27ter / V29 on equipment
V23 ----> 0.9 s
Case N "2 - delayed connection at 1200/75 bps of equipment (" Minitel ") V23 / V27ter / V29 on equipment
V23 ----> 2.1 s note: From "Minitel" 2, the connection time is 1.8 s.

Attempting to connect a V23 device to a V27ter or V27ter / V29 device is meaningless and will always lead to a connection failure. It is the same for a V27ter or V27ter / V29 equipment calling equipment only V23.

In these cases, the phone line automatically disconnects after a given timeout (40 sec).

V29 modulation connection
Case N "7 - Early connection to 9600 bps of equipment (" Minitel ") V23 / V27ter / V29 on equipment
V27ter / V29 ----> 1.38 s
Case N "8 - delayed connection to 9600 bps of equipment (" Minitel ") V23 / V27ter / V29 on V27ter / V29 equipment ----> 0.9 to 3 s connection in V27ter modulation
Case N "3 - Early connection to 4800 bps of equipment (" Minitel ") V23 / V27ter on equipment
V27ter or V27ter / V29 ----> 2.4 s
Case N "4 - delayed connection to 4800 bps of equipment (" Minitel ") V23 / V27ter or V23 / V27ter / V29 on a V27ter equipment ----> 1.9 to 3.9s
Case N "5 - delayed connection to 4800 bps of equipment (" Minitel ") V23 / V27ter on V27ter / V29 equipment ----> 1.9 to 9s
Case N "6 - Early connection to 4800 bps of equipment (" Minitel ") V23 / V27ter / V29 on equipment
V27ter ----> 2.9s
Case N "14 - connection to 4800 bps of equipment (" Minitel ") V23 / V27ter / V29 or V23 / V27ter on EBS

TRANSPAC ----> 15s.

In the case No. 1 (FIG. 2) after a line seizure following a DLT request to which the called equipment responds with 3.3 s of 2100 Hz, the connection command issued by the calling equipment "MINITEL" operating only in V23 mode, or in
V23 and V27ter, or even in V23, V27ter and
V29, is followed by detection by the latter whose modem is in reception mode of at least 300 ms of the 2100 Hz frequency transmitted for 3.3 s by the called V23 equipment ("PAVI"). according to the invention of 75 ms of silence after the emission at 2100
Hz is used to validate the known connection procedure according to the V23 mode (detection by the calling device of at least 80 ms of a signal at 1300 Hz transmitted for 40 seconds by the "PAVI-V23", and transmission by calling equipment with a frequency of 390 Hz, and establishment of the full duplex connection ("fullduplex").

Case No. 2 (Figure 3) corresponds to a delayed connection The connection order occurs after the end of the 2100 Hz emission (or too late for the calling equipment to detect 300 ms of the 2100 Hz frequency In this case, the calling equipment identifies a device V23 called, by detection (known per se) of 1.8 seconds signals at 1300 Hz.

Case No. 3 (FIG. 4) corresponds to the anticipated connection of a V23 / V27ter "MINITEL" to a device responding in V27ter mode.After detection of 300 ms at the 2100 Hz frequency, the calling equipment detects a silence of 150 ms, indicating that the communication will not be in V23 mode The calling equipment sends a long TL V27 train (including segments 1 and 2) and the called equipment detects the frequency of the carrier (1800 Hz) which characterizes the mode V27ter (detection of 100 ms of 1800 Hz of the segment 1) The equipment called (for example PAVI V27ter or V27ter / V29) positions (if necessary) its modem in V27ter mode and then emits a long train TL V27 (including segments 1 and 2) which is received by the calling equipment. If this reception is valid, the connection is established (each device has transmitted and received a long TL V27 train) and the communication is established by exchange of TC short trains
V27 in V27ter mode (without segments 1 and 2). During the exchange of TC V27 short trains, the connection is established first at the frame level (LAPX), then at the packet level (X25) in a manner known per se.

Case # 4 (Figure 5a) corresponds to a delayed connection to a V27ter equipment. In a call-out order and without transmission of the calling equipment, the called equipment transmits, after a time interval of 200 ms after the end of the 2100 Hz (3.3s) emission, a alternating long trains TL V27 and short trains TC V27 at a rate of 2 seconds (until a delay time of 40 seconds elapses after which, in the absence of a successful connection, the called equipment automatically releases the link) .

After the connection order, the calling equipment in reception mode, detects 100 ms of the frequency 1800 Hz of the first long train TL V27 it receives and following this reception, it sends in turn a long train TL 27 which is received by the called equipment. The connection is established at the physical level, each of the equipment having emitted and received a long train V27.

The communication continues in V27ter mode by exchanging TC V27 short trains and establishing the synchronization of the higher levels (frame and packet).

Case n 4bs (Figure 5b) differs from the previous one in that the calling Minitel operates at least in different modes.
V27ter / V29 while called equipment does not operate in V29 mode. The calling equipment detects the characteristic 1800 Hz frequency of the V27ter mode, but in response, it sends this time a V29 long train to make a V29 connection attempt.

Called equipment not recognizing the long train
V29, transmits again a long train V27ter, to which the calling equipment responds by a long train V27ter, which allows the establishment of the connection. This procedure makes it possible to check whether the called equipment is likely to connect in V29 mode (see further case ne9).

Case No. 5 (FIG. 6) corresponds to a delayed connection to a V29 / V27ter device After the silence of 200 ms following the emission at 2100 Hz, the called equipment tries to establish the communication in V29 mode.

The calling equipment V27ter / V23 remains "mute" because its modem, in reception mode after the connection order, does not recognize the carrier frequency V29 (1700 Hz) in segment 1 of the TLV29 trains. After three unsuccessful attempts in V29 mode (6 seconds in total), the called equipment transmits a long TL V27 train whose unshielded 1800 Hz carrier of segment 1 is detected by the modem of the calling equipment which in turn transmits a TL V27 long train whose unmodulated carrier at 1800 Hz is detected by the modem of the called equipment. The connection is then established at the physical level, and continues by exchanging TC V27 short trains and establishing higher levels (frame and packet).

According to the nabis case (FIG. 6b), the calling equipment is capable of recognizing the frequency of 1700 Hz, although it does not operate in the V29 mode, (it suffices to add an additional filter to the modem), and it transmits directly a V27ter long train, hence a much faster connection than in case 5, by exchange of two V27ter long trains.

Case No. 6 (Figure 7) concerns the early connection of a calling device V29 / V27ter or V29 / V27ter / V23 to a device called V27ter, after detection of 150 ms of silence after detecting 300 ms of 2100 Hz. The calling equipment sets its modem in transmission mode V29 and transmits a long train TL V 29. The called equipment does not recognize a long train TL29, it in turn transmits, after a delay of 2 seconds, a long train TL V27. calling equipment detects 100 ms of the frequency 1800 Hz of segment 1 of long train TL
V27 and position its modem in V27ter mode. The duration of the segments 1 and 2 allows this operation to be performed before the arrival of the segment 3. The calling equipment therefore recognizes the long train TL V27 and response in turn a long train TL V27. Communication is established at the physical level, and continues as before (exchange of short trains ...).

Case No. 7 (FIG. 8) is similar to case No. 3, except that the communication is established in mode V29 in which the two devices can operate.

Case # 8 (Figure 9a) is similar to Case # 4 except that communication is established in V29 mode.

Case No. 9 (FIG. 9b) is close to the Nabis and No. 8 cases, but the delayed connection order occurs while the called equipment transmits long trains in the V27ter fallback mode, after three transmission attempts. long trains V29. In this case, the calling equipment sends a long train V29 which allows the establishment of communication in V29 mode.

Case No. 10 (FIG. 10) concerns a process of resumption of transmission in V27ter mode (without change of mode) After reception of three non-compliant TC27 short trains, a piece of equipment (here the calling equipment) resumes the process of learning in V27ter modulation by emitting a TL V27 long train.

The called equipment, whose modem in receive mode continuously searches for the unmodulated carrier frequency, detects the frequency 1800 Hz in segment 1 of the long train TL V27, which enables it to identify the recovery process (the trains short do not have segments 1 and 2). He receives the long train
TL V27 and in turn transmits a long TL V27 train that is received by the calling equipment. The recovery process has been completed and the communication continues by exchanging TC V27 short trains. This process does not disrupt the higher levels (trains and packets) because no disconnect signal is issued. The recovery process has a duration less than an automatic disconnection delay of the higher levels for which everything happens as if it were happening delaying the sending of information.

Case No. 11 (FIG. 11) is similar to case ne10, except that the resumption is carried out in mode V29 (without change of mode) with detection of the unmodulated 1700 Hz frequency (segments 1 and 2 of TL V29) by the equipment called.

Case No. 12 (Figure 12a) describes a recovery process with mode change after receiving three non-compliant TC V29 short trains (eg line disturbance), equipment (here calling equipment) resumes the process. V29 modulation by transmission of a long train TL V29 This attempt being unsuccessful (here only one attempt), the calling equipment transmits a long train TL V27 whose carrier frequency of the segment 1 is detected by the This device positions its modem in V27ter mode before receiving segments 3 to 5 of the TL V27 long train, and in turn transmits a long TL V27 train which is received by the called equipment. short TC V27 without disturbance of the higher levels (frame and packet) due to their compatibility to a few parameters.

Case No. 12bis (FIG. 12b) corresponds to the previous case, but the learning process is repeated twice in V29 mode (two attempts) and twice in V27ter mode (two attempts).

Case No. 13 (Figure 13) concerns an aborted recovery from a V29 mode communication A device (eg calling equipment) receives three non-conforming TC V29 short trains. V27ter mode (as in the full case) After receiving two non-compliant TL V27 long trains (two attempts), the calling equipment interrupts the call.The number of two attempts is given as an example, but it can be considered to make a single attempt.

Case No. 14 (Figure 14) relates to the connection to a synchronous standardized input (EBS) of the current network
TRANSPAC, in V27ter mode. The process starts as in case No. 7. The long train TL V29 (or possibly TL V27) is not recognized by the receiver EBS, which transmits a long train (TL 27 fallback) corresponding to a fallback mode at 2400. bps then short trains (TC V27 fallback) corresponding to the fallback mode.The calling equipment receiving no known mode for a delay time of 10 seconds (failure to detect the unmodulated carrier), it automatically programs its modem in reception of long trains TL V27 without segments 1 and 2, that is to say that it suppresses the logical condition of detection of the frequency of the unmodulated carrier. The duration of 10 seconds is sufficient to discriminate this case with respect to others (in particular Case No. 5).

Case No. 15 (FIG. 15) relates to the known procedure for switching to the voice-data mode with the V23 modulation.

The called equipment issues a tilt sequence in speech mode for N seconds. A disconnection is performed by dropping the carrier without breaking the telephone link and an audible message is transmitted for a selected delay time. When the timer expires, the complete connection is again performed in a conventional manner (equipment
MINITEL V23).

Case No. 16 (Figure 16) relates to a phonedonne process according to the invention in V29 modulation.The voice switching sequence produces a logical disconnection with release of the higher levels (packet and frame) and physical disconnection by falling of the carrier. An audible message is emitted during a given delay interval (telephony mode) When the timer expires, the connection is resumed in V29 mode on the initiative of the called equipment (TL V29 transmission) and the physical connection is established. after an exchange of TL V29 long trains, then at the packet and frame level in the following TC V29 short trains for a restoration of the previous V29 modulated state.

Case No. 17 (FIG. 17) is analogous to the procedure except that the given mode is the V27ter mode folded back from the V29 mode.After the reconnection in the given mode, the called equipment attempts a recovery in V29 mode. this attempt, recovery is performed in V27ter fallback mode significantly less sensitive to disturbances of the line.

Case No. 18 (FIG. 18) is analogous to case ne17, but recovery in V29 mode is successful and the connection is made physically in long trains TL
V29, then at the frame level and at the packet level in the following TC V29 short trains.

Case No. 19 (FIG. 19) also relates to a voice-data process, in which the calling equipment makes an anticipated request to return to communication in data exchange mode, before the end of the time-out period of N seconds of the mode. This anticipated demand is manifested in the form of the transmission of an unmodulated carrier segment 1 V29, to which the called equipment responds by an attempt to connect in V29 mode (transmission of long trains V29). In this case, the connection can not be established in V29 mode, the called equipment then transmits V27ter long trains (fallback mode) leading to a synchronization in V27ter mode, it will be noted that the anticipated demand for return in exchange mode. of data by a V27ter-only device is effected by the transmission of an unmodulated carrier segment 1 V27ter.

Case 20 (FIG. 20) is analogous to case 19, except that the return to data exchange mode is successful in mode V29.

Figs. 21a to 21s provide the write instructions for the basic operations implemented in the sequencer, from the ROCKWELL R96-VFX modem instruction set, for V27ter or V29 operation. These instructions are implemented in the next higher level sequences of FIGS. 22a to 22d, for the emission of the long and short trains in V27ter and V29, and for the reception of these trains in FIGS. 23a to 23d, for which it will be noted in particular the characteristic signals VRECTL V29 and VRECTC V29,
VRECTTL V27 and VRECTTC V27 characterizing the correct reception (= OK) respectively of a long train V29, a short train V29, a long train V27ter and a short train V27ter.

FIGS. 24 to 24d further characterize the end of transmission phases of such trains and FIGS. 25a to 25f, the end of reception of such trains, FIG. 25c to f concerning the case of long or short trains presenting application data. (flag or "flags" and data).

The automaton of FIG. 26a comprises a sequence of operation in local mode, making it possible to switch following an order of connection OC sent or received, either to a connection automaton in calling mode AC1, or to a connection automaton in called mode AC2, which are also connected to an ACV23 communication controller in V23 mode. Each of the automata
ACl and AC2 is connected to an ACV27ter controller in
V27ter and / or a PLC in V29 ACV29 mode.

The ACV29 PLC is connected to a V29 ARV29 recovery controller, to allow one or more retry-adaptation attempts in V29 mode which can also be connected to a fallback controller.
AREP allowing a fallback to the ACV27 PLC.

The ACV27 controller may also be equipped with an ARV27 V27 recovery controller to allow one or more replay-adaptation attempts in the same mode.
V27ter. The ACV27 and ACV29 controllers are also connected to an APH PLC allowing a passage in voice mode, which in turn is connected to an APHD PLC for voice-data switching for a return to a positioning either in V29 mode (PLC ACV29) or in V27ter mode (PLC ACV27).

In addition, the line can be released (return to "local" mode) from the controllers ACV29, ACV27, ARV27 and
APHD.

According to FIG. 26b, the PLC in calling mode (left column) after the connection command that it sends following a telephone line seizure at its initiative, with a delay (90 s) and programs the simultaneous detection by the multi-frequency modem (1300 Hz, 1700 Hz, 1800 Hz, 2100 Hz) (Figure 27b). The PLC in called mode allows, after a received connection command, with a connection delay (40 s) and emits a response tone (2100 Hz) (see point 1, figure 28a).

With regard to the connecting machine in the calling mode (FIGS. 27a to 27g), a general diagram is given in FIG. 27a. The left branch represents a connection in V27ter mode (detection of 1800 Hz) and the right branch in V29 mode (detection of 1700
Hz). Figure 27b shows the branch performing the detection of the characteristic frequencies of each modulation. If detection of 300 ms of 2100 Hz (so-called anticipated connection), passage to point B (Figure 27c), then in the absence of 1300 Hz which would characterize a V23 mode, passage from point F (Figure 27d) to transmit a long train V29. If detection of 1700 Hz, transition to point D (Figure 27f) for establishment of the communication in V29 mode. If detection of 1800 Hz, passage to point C (Figure 27e), and emission of a long train V27ter (because no previous transmission of long train V27ter) and communication in V27ter (signal
COM V27-1 - see fig. 30c and 30d). Figure 27c shows the sequencing from point B of Figure 27b (300 ms detection of 2100 Hz) and leading to either a connection attempt at V23 (20 ms at 1300 Hz) or at point F (Fig. 27d) . From point F (fig 27d), and after detection of 150 ms of silence, connection attempt in V29 and connection in V29 mode (point D and fig 27f) or in V27ter mode (point
G and fig 27e).

In Fig. 27e, in case of erroneous reception of a long train V27ter, new connection attempts (point G of Fig. 27d) and release of the link at the expiry of the delay of 15 s. In FIG. 27f, in case of erroneous reception of a long train V29, a new connection attempt (point G of FIG. 27d) in
V29 and / or V27ter until expiry of the time delay. In Figure 27e, after successful reception of a long train V27ter, and in the absence of long train previously emitted and 2100 Hz previously detected, transmission of a long train V29 (Figure 27g, point H) in order to a so-called delayed connection in V29 according to case No. 9.

To obtain a single-mode automaton, it suffices in FIGS. 27a to 27g to delete the sequences corresponding to the unused mode (emission of the long and short trains, detection of the unmodulated carrier frequency).

The called-mode connection automaton, whose general diagram is given in FIG. 28a, comprises the sequences making it possible to discriminate between the modes
V23, V27ter and V29, a V29 mode handshaking sequence being shown in Figure 28c, in V27ter mode in Figure 28d, and in V23 mode in Figure 28e. As before, the operation in two modes or in a single mode (V27ter or V29) can be obtained by removing from the sequencer the superfluous elementary sequences.

In FIG. 28b, the NB PASSAGE parameter makes it possible to make several attempts (3) to connect in V29 mode and / or in V27ter mode by transmitting a long train without valid reception of a long train back (point 6 of the fig 28b, 28c and 28d).

The voice-data switching sequencer is represented in FIGS. 29a to 29c, and allows a new setting in communication in V29 mode through sequences of FIG. 28c and in V27ter mode through the sequences of FIG. 28d, however, this does not imply that the equipment includes the entire called-mode connection controller. The same is true for the procedure for releasing the link FIG. 29b (point 6 of FIG. 29a).

The V29 modulating adaptation communication and recovery automaton (FIGS. 30a to 30b) makes it possible to perform resumption-adaptation in the same mode, or else in the V27ter fallback mode. The recovery-adaptation automaton also ensures short train transmissions after communication (COM V27-1, COM V27-2,
COM V29-1 and COM V29-2). The NB PASSAGE parameter makes it possible to carry out several attempts (here 2) of readaptation in V29 (FIG. 30b) and / or V27TER (FIG. 30d).

The two automata (vertical branches of FIGS. 30a and 30c) ensure the sending of short trains V29 and V27ter and activate the short-circuit resumption-adaptation sequences (VRECTCV29 = OK or VRECTCV27 = OK).

Claims (17)

1. A method for setting in half-duplex communication two equipment A and B through a telephone line, characterized in that the two devices are arranged, after establishment of the telephone connection, to communicate according to at least one transmission mode. in duplex mode and in that the method implements at least one exchange of tuning signal streams, for communication in a duplex transmission mode, each signal train of tuning starting with an unmodulated carrier signal of given nominal duration having a characteristic carrier frequency of said requested transmission mode and having at least one conditioning segment, and in that each of the two devices is arranged to detect the frequency of said unmodulated carrier signal characteristic of said transmission mode used and that both equipment A and B are arranged to perform the exchange of two sets of tuning signals according to the following steps: a) transmission by one of the equipment called "first equipment for tuning" of at least a first signal train of tuning according to a given mode of duplex transmission alternately. b) analysis by the other equipment referred to as "second equipment for tuning" the frequency of the unmodulated carrier signal of said first tuning signal stream. c) in case of recognition by the second equipment of the frequency of the carrier signal of said given transmission mode, positioning of the second equipment in reception, according to said transmission mode, said conditioning segment. d) validation by the second equipment of the reception of said conditioning segment of the first set of tuning signals, and conditioning of the second equipment according to said given transmission mode. e) transmission by the second equipment of a second train of tuning signals according to the recognized transmission mode which corresponds to the given mode, which validates by the second equipment setting in communication according to the given mode of transmission. f) the first equipment analyzes the frequency of the unmodulated carrier signal of the second signal stream. g) in case of recognition by the first equipment of the frequency of the carrier signal of the given transmission mode, maintaining the positioning of the first equipment in reception in said given transmission mode recognized and accepted by the second equipment. h) validation by the first equipment of the reception of said conditioning segment of the second train of tuning signals, and conditioning of the first equipment according to said given transmission mode. i) validation by the first equipment of the setting in communication according to said given mode of transmission. 2. Method according to claim 1, characterized in that the equipment A is arranged to communicate according to a first mode of transmission and a second mode of transmission duplex duplex less rapid than the first mode of transmission, in that the equipment B is arranged to communicate according to said second transmission mode but is not arranged to communicate according to said first transmission mode and that the equipment A and B are arranged to perform the exchange of two trains of tuning according to the following steps - steps a) and b), wherein the given transmission mode is the first mode of transmission. j) in case of non-recognition by the equipment B of the frequency of the unmodulated carrier signal according to the first mode of transmission and the impossibility of the equipment B to be positioned according to said first transmission mode, non-validation by the equipment B of the reception of the first train of tuning signals. B and the second equipment is equipment A. k) steps a) to i) in which the given mode of transmission is the second mode of transmission, during which the first equipment is the equipment 3. Method according to claim 1, characterized in that the second equipment is the equipment B and is arranged to communicate according to said first transmission mode and a third half-duplex transmission mode faster than the first one. transmission mode and, in that the first equipment is the equipment A and is arranged to communicate only according to said third transmission mode. 4. Method according to claim 1, characterized in that each of the equipment A and B is capable of functioning either as first equipment or as second equipment. 5. Method according to one of claims 1 to 4, characterized in that the unmodulated carrier signal is an echo cancellation segment used as a discriminant of the duplex transmission mode. 6. Method according to one of claims 1 to 5, characterized in that said validation of the setting in communication by the equipment validating the reception of the second train of signals of agreement, comprises the emission of a train of signals of synchronization not starting with an unmodulated carrier signal. 7. Method according to one of claims 1 and 3, characterized in that a communication request is immediately following a request for establishment of the telephone connection by the equipment A and in that the equipment A and B are arranged to carry out the following preliminary steps oo) request for establishment of the link by the equipment A.  1-0) detection by the equipment B of the request for establishment of the link and establishment of the link. 2-O) transmission by the equipment B of a first signal of duration at least equal to a first given duration, of frequency equal to that of the response tone of an automatic response data equipment, having a different frequency d a half-duplex modulation carrier signal frequency followed by a second duration silence.  3-O) detection by the equipment A of the presence of said frequency signal during at least said first given duration. 4-O) measured by the equipment A of the second duration of said silence.  5-O) if the second duration is greater than a given duration threshold, enabling the execution of steps a) to i) of claim 1 or steps a) to k) of claim 2, for which the first equipment is equipment A and the second equipment is equipment B. 8. Method according to claim 7, characterized in that the equipment A and B are arranged to perform the communication in a non-duplex duplex transmission mode if, after step 4-O) of the claim 7, the equipment A measures a second duration of silence below a threshold of given duration. 9. Method according to one of claims 1, 3, 4 or 5, characterized in that a placing in communication order is not immediately consecutive to establishment of the connection by the equipment B, which is consecutive to a request for establishment of the connection by the equipment A, in that the order of communication occurs during a transmission sequence by the equipment B of tuning signal trains according to the given mode of transmission, and in that said transmission sequence constitutes said step a), the first equipment being thus the equipment B and the second equipment, the equipment AT. 10. Method according to one of claims 1 to 5, characterized in that a placing in communication order is not immediately consecutive to an establishment of the connection by the equipment B, which is consecutive to a request for establishment of the link by the equipment A, in that the order of communication occurs during a transmission sequence by the equipment B of tuning signal trains according to said second transmission mode slower than said first mode of transmission and in that it comprises the implementation of steps a) to i) according to the first transmission mode, in which the first equipment is the equipment B and the second equipment is the equipment A.  11. Method according to one of claims 1 to 5, characterized in that a placing in communication order is not immediately consecutive to a establishment of the link by the equipment B, which is consecutive to a request for establishment of the link by the equipment A, and in that the communication order occurs during a transmission sequence by the equipment B of tuning signal trains according to said first plus transmission mode. fast than said second transmission mode, in that the equipment A is arranged to communicate according to said second mode but not according to the first mode, and in that the equipment B is arranged to communicate both according to the first and the second mode. second mode, and in that the equipment A is arranged to analyze the carrier frequency according to the first mode, and in that it comprises the following steps  - Analysis by the equipment A of the carrier frequency of a said train of tuning signals,  in the case of recognition of said frequency according to the first transmission mode, validation of steps a) to i) according to the second transmission mode, during which the first equipment is equipment B and the first equipment is equipment A .  12. The method of claim 1, characterized in that the equipment A and B are arranged to perform before step a), the following preliminary steps  12-1) sending by the equipment A a first train of tuning signals according to the first transmission mode.  12-2) analysis by the equipment B of the presence of the frequency of the carrier signal.  12-3) in case of non-recognition by the equipment B of the frequency of the carrier signal corresponding to the second transmission mode, after a waiting time greater than a given duration threshold, validation of the execution of the step a) to i) according to the second transmission mode, in which the first equipment is the equipment B and the second equipment is the equipment A. 13. Method according to one of claims 1 to 6, characterized in that said setting in communication is consecutive to a passage in speech mode and in that it comprises the following preliminary steps 13-1) release of the communication duplex to the alternating successively with the logical levels of the communication protocol and then with the physical level while maintaining the telephone connection between the two equipments. 13-2) change to speech mode for a given delay time. 13-3) detection of the end of the delay time. 13-4) validation of the execution of steps a) to i) of claim 1 or steps a) to k) of claim 2. 14. Method according to claim 13, characterized in that the equipment A and B are arranged to detect the frequency of said unmodulated carrier signal characteristic of at least one transmission mode as well as in voice mode and in that the equipment A and B are arranged to perform after the steps 13-1 and 13-2, the following steps 14-1) before the end of the delay time relative to the speech mode, initialization by one of the equipment of the setting in communication, by issuing a placing in communication order during the voice phase. 14-2) validation of the execution of steps a) to i) of claim 1 or steps a) to k) of claim 2. 15. Equipment for implementing the method according to one of the preceding claims and comprising a line interface and a modem programmed by a sequencer characterized in that said sequencer is arranged to 15-1) program transmission by the modem of a tuning signal stream preceded by an unmodulated carrier signal; 15-2) scheduling the modem to detect at least one unmodulated carrier frequency at the beginning of a matching signal stream; received, and for positioning the modem in a duplex transmission mode corresponding to said carrier frequency, so as to allow the modem to receive the other signals of said received tuning train, and 15-3) to program a validation of the physical duplex communication in alternate mode according to said mode of transmission once the modem has received and transmitted in a conforming manner a said train of tuning signals, and then perform an exchange of two synchronization trains to validate a connection in a first mode.  16. Equipment according to claim 15, characterized in that the sequencer is arranged so that, when the modem is in reception mode, said detection of at least one unmodulated carrier frequency is carried out continuously.  17. Equipment according to one of claims 15 or 16, characterized in that said sequencer is arranged to validate said transmission by the modem of a train of matching signals according to 15-1 when one of the following conditions is fulfilled.  - compliant reception of a signal stream according to 15-2,  - Detection by the modem following a request to set in communication a characteristic silence interval of said duplex transmission mode.