Multiplex communications – Duplex – Convertible to half duplex
Patent
1995-06-29
1999-02-02
Olms, Douglas W.
Multiplex communications
Duplex
Convertible to half duplex
370286, 370478, 375222, H04J 1500, H04L 500
Patent
active
058674870
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The object of this invention is a method of automatic duplex or semi-duplex (called half-duplex) communication of a mono-mode or multi-mode unit and a mono-mode or multi-mode unit for modulation such as, for example, V23, V27ter and V29 via a general telephone network with switching and over station to station telephone circuits, such as two-wire leased circuits.
BACKGROUND
Since Jul. 1, 1980, the date of the first testing of the electronic directory service at Saint Malo, the Minitel has been using, in France, a transmission speed of 1200 bps to receive reference service information and a speed of 75 bps to transmit keyboarding of the user. This mode of transmission, in full duplex, is based on V23 modulation which is a speed of 1200/75 bps between the Minitel and Videotext Access Point (PAVI) units. The connection between Minitel and PAVI is based on the switched telephone network (RTC). The connection between PAVI and the Teletel servers is based on the TRANSPAC network with transmission speeds of 19.2 kbps or 48 kbps.
At the beginning of the 1990s, in order to improve convenience and speed in consulting Teletel services, provision was made to increase the transmission speed at first to 4800 bps, and then to 9600 bps between the Access Point and Minitel. This new mode of transmission in semi-duplex or half-duplex is based on the V27ter modulation for the speed of 4800 bps and on the aforementioned V29 modulation at 9600 bps. The V27ter and V29 standards have been kept for reasons of cost and performance. The speed of 4800 bps and 9600 bps can be used over the two paths, the data circuit termination unit (ETCD) or modem operating at half speed.
This new Teletel access service, called "Teletel high speed" access service (or TVR) thereby allows a useful rate of flow of communication multiplied by four in V27ter and by eight in V29 with respect to a useful throughput rate of V23 access. It thus permits a rapid transfer of pages requiring a considerable volume of information; this is the privileged channel for operation of the future photographic Minitel and for applications such as transfers of files, telecopy, audio videotext, etc.
The main public terminal (or Minitel) is not currently connectable, equally and without specific intervention of the user, over the Teletel V23 access, over V27ter Teletel access and over the forthcoming V27ter/V29 accesses with connection time similar to the present V23.
Establishment of telephone connection between the Minitel and videotext access points (PAVI) is effected principally over the switched telephone network (RTC).
Request for establishing connection consists of the actions of picking up the telephone line (or going on line) and dialing the number. This request can be at the initiative: LECAM.
Sensing this request for establishing communication by the distant unit (calling ring over the switched telephone network (RTC) or location of an indicator on the shared line) authorizes it to effect connection.
After making the connection, communication or physical connection is effected by the exchange and recognition of signals between the modems and the two units. Validation of communication allows the two units to then transmit data and to thereby establish a logical connection such as the establishment of packet and screen levels of the communication protocol used, in V27ter and in V29 for example.
The request for communication (or "order to establish communication" or even "connection order") can be at the initiative: Minitel, directory, sequence.
To communicate in V23, V27ter or V29 mode (V23/V27ter/V29) it is possible to use several "end-connection" buttons one time for each of the modes. This manual solution is not ergonomic for a large public user group.
Another solution would be to rely on preliminary and systematic communication in V23, and then, by reception of a particular sequence, to change over to V27ter or V29 transmission. This solution would be penalized in connection time, and would not allow communication with existing units e
REFERENCES:
patent: 4625276 (1986-11-01), Benton et al.
patent: 4694450 (1987-09-01), Staab
patent: 4764940 (1988-08-01), Paneth et al.
patent: 5095494 (1992-03-01), Takahashi et al.
patent: 5245441 (1993-09-01), Ruben
Danneville Bernard
Martiniere Jean-Pierre
Normand Olivier
France Telecom
Hom Shick
Olms Douglas W.
Telediffusion DeFrance
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