EP0332792A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Data transmission system connectable to the telephone switched network
Assignee: International Business Machines Corp
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Filing: 1988-03-15
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Granted: —
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Expires: 2008-03-15
Abstract
Abstract Data transmission system including a switching circuit (20) which enables the connection of a tributary modem to a control modem by means of the public switched network when it is no longer possible to transmit data on the leased network because the line associated to the tributary modem has failed. The switching circuit connects both the permanent leased line and the switched network to the receiver (16) of the control modem. It comprises a narrow pass-band filter (31) which is permanently connected between the reception side of the switched network and the control modem receiver (16). When the tributary modem answers after a call from the control modem, it sends a tone ahead the data message the frequency of which corresponds to the frequency of the pass-band filter (31) and is out of the data band. Such a tone being detected by the pass-band filter (31), the control modem toggles a two position switch (30) which isolates the leased line and connects the switched network to the receiver (16) of the control modem.
Inventors
- 👤 François Caron
- 👤 Jean Cholat-Namy
- 👤 Emile Morlec
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-30 10:32
CPC Classifications
H; H04; H04M; H04M11/00; H04M11/06; H04B; H04B1/00; H04B1/74; H04L; H04L12/00
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
275 words
Data transmission system connectable to the telephone switched network, comprising a control device (11) including a transmitter (12) and a receiver (16), a plurality of tributary stations also including each a transmitter and a receiver, and a permanent transmission network for exchanging data between said control device and each of said plurality of tributary stations, said permanent transmission network including a principal link connected to said control device and tributary links each one being connected on the one hand to one of said tributary stations and on the other hand to said principal link according to a multipoint configuration, said control device comprising a switching circuit (20) enabling said control device to be connected to the telephone switched network so as to continue exchanging data with one tributary station (41) the tributary line of which has failed; said system being characterized in that said switching circuit is comprised of : connections (17, 18) for permanently connecting the transmitter of said control device to the transmitting side of said telephone switched network, as soon as said control device has been warned that said tributary link has failed; a detecting circuit (31) connected between the receiving side of said telephone switched network and the receiver of said control device, adapted to detect a heading signal transmitted by the tributary station associated with said failed tributary link; and a two-position switch (30) controlled by said control device for disconnecting the receiver of said control device from the receiving side of said principal link and connecting it to the receiving side of said telephone switched network in response to the reception of said heading signal by said control device.
Claim 2
Dependent Claim
275 words
Data transmission system connectable to the telephone switched network, comprising a control device (11) including a transmitter (12) and a receiver (16), a plurality of tributary stations also including each a transmitter and a receiver, and a permanent transmission network for exchanging data between said control device and each of said plurality of tributary stations, said permanent transmission network including a principal link connected to said control device and tributary links each one being connected on the one hand to one of said tributary stations and on the other hand to said principal link according to a multipoint configuration, said control device comprising a switching circuit (20) enabling said control device to be connected to the telephone switched network so as to continue exchanging data with one tributary station (41) the tributary line of which has failed; said system being characterized in that said switching circuit is comprised of : connections (17, 18) for permanently connecting the transmitter of said control device to the transmitting side of said telephone switched network, as soon as said control device has been warned that said tributary link has failed; a detecting circuit (31) connected between the receiving side of said telephone switched network and the receiver of said control device, adapted to detect a heading signal transmitted by the tributary station associated with said failed tributary link; and a two-position switch (30) controlled by said control device for disconnecting the receiver of said control device from the receiving side of said principal link and connecting it to the receiving side of said telephone switched network in response to the reception of said heading signal by said control device.
Claim 3
Dependent Claim
36 words
System according to claim 1 wherein said heading signal is a tone the frequency of which is out of the data band, and said detecting circuit (31) is a pass-band filter adapted to detect said tone.
Claim 4
Dependent Claim
49 words
System according to claim 1 or 2 wherein said control device is a control modem (11), said tributary stations are tributary modems (41) in a multipoint configuration, said principal link (13, 15) being a leased link for exchanging data between said control modem and each of said tributary modems.
Claim 5
Dependent Claim
28 words
System according to claim 3 wherein the telephone switched link used for exchanging data between said control modem (11) and said tributary modems (41) is a two-wire link.
Claim 6
Dependent Claim
167 words
System according to claim 4 further comprising a two-position switch (50) in the tributary modem (41) the associated link (13′) of which has failed for connecting the receiving part of said tributary modem to said two-wire link of the telephone switched network as soon as said control modem is warned that said associated link has failed; a normally closed switch (60) in said control modem (11) connecting the transmitting part (12) of said control modem to said two-wire link, said switch being opened when said tributary modem transmits data to said control modem so as to cut off the transmission of the continuous carrier from said control modem to said tributary modem; and a normally closed switch (70) in said tributary modem connecting the receiving part of said tributary modem to said two-wire link, said switch being opened when said tributary modem transmits data to said control modem in order to avoid said receiving part receiving data sent by the transmitting part (42) of said tributary modem.
References Cited (Backward Citations)
No citation records indexed.
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