US3639904A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Data communication system of loop configuration and serial transmission of time slots
Assignee: International Business Machines Corp
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Filing: 1970-05-05
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Granted: 1972-02-01
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Expires: 1990-05-05
Abstract
Abstract In a data communication system a plurality of remote stations and a central station are arranged in a series loop. The central station transmits a succession of time slots to the loop and information is transferred between the central station and the remote stations with character interleaving under control of the central station. Each remote station includes one or more terminals. A terminal wishing to transmit a message sends a request-for-service signal to the central station in the first free time slot received by its remote station. The terminal cannot transmit a message or a further request-for-service signal until it receives a proceed signal from the central station. After receiving a proceed signal the terminal can transmit a message. At the end of the message the terminal is again locked out (i.e. it cannot transmit message data) but remains free to transmit a request-for-service signal by which means it may again obtain a line position.
Inventors
- 👤 Jeganandaraj A Arulpragasam
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-22 21:52
CPC Classifications
H; H04; H04L; H04L12/00; H04L12/28; H04L12/42; H04L12/423
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
253 words
A data communication system comprising: a central station; a plurality of remote stations, each remote station including at least one terminal, some at least of said terminals serving as input terminals for the system; transmission means interconnecting said remote stations and said central station in a series loop; means at said central station for transmitting serially to a first remote station in the loop a plurality of time slots each being in either a free state, in which it is available to receive data from a remote station, or a busy state in which it is not so available; means at each of the remote stations for receiving and examining said slots, for selectively altering the content of said slots and for transmitting said slots to the next device in the series loop which may be another of said remote stations or the central station; request means at each of said input terminals actuable to enter a request-for-service signal in a free time slot received by the input terminal''s associated remote station after actuation of the request means, and lockout means associated with each of the input terminals operative to prevent input of data to the system via said terminal after its request means have been actuated and before there is received by its associated remote station a slot bearing a proceed signal addressed to said terminal by the central station in response to said request-for-service signal; the lockout means being disabled upon receipt of said proceed signal by said associated remote station.
Claim 2
Dependent Claim
253 words
A data communication system comprising: a central station; a plurality of remote stations, each remote station including at least one terminal, some at least of said terminals serving as input terminals for the system; transmission means interconnecting said remote stations and said central station in a series loop; means at said central station for transmitting serially to a first remote station in the loop a plurality of time slots each being in either a free state, in which it is available to receive data from a remote station, or a busy state in which it is not so available; means at each of the remote stations for receiving and examining said slots, for selectively altering the content of said slots and for transmitting said slots to the next device in the series loop which may be another of said remote stations or the central station; request means at each of said input terminals actuable to enter a request-for-service signal in a free time slot received by the input terminal''s associated remote station after actuation of the request means, and lockout means associated with each of the input terminals operative to prevent input of data to the system via said terminal after its request means have been actuated and before there is received by its associated remote station a slot bearing a proceed signal addressed to said terminal by the central station in response to said request-for-service signal; the lockout means being disabled upon receipt of said proceed signal by said associated remote station.
Claim 3
Dependent Claim
36 words
A system as claimed in claim 1 wherein: each request means is operative to enter the request-for-service signal in the first free time slot received by its associated remote station after actuation of said request means.
Claim 4
Dependent Claim
38 words
A system as claimed in claim 2 wherein: each of said input terminals includes a keyboard and which is actuable to input data to the system, and said lockout means includes means for preventing actuation of said keyboard.
Claim 5
Dependent Claim
76 words
A system as claimed in claim 1 wherein: each of said input terminals includes a keyboard which is actuable to input data to the system, and said lockout means includes an electronic latch (herein called an enter latch) activatable by said proceed signal, and means for preventing actuation of said keyboard; said means for preventing actuation of the keyboard being normally operative but being rendered inoperative when the enter latch is activated by the proceed signal.
Claim 6
Dependent Claim
52 words
A system as claimed in claim 4 wherein: the enter latch is resettable by an end-of-message signal indicating that input of data from said input terminal has been completed, at least temporarily, said means for preventing actuation of the keyboard being rendered operative again upon resetting of the enter latch as aforesaid.
Claim 7
Dependent Claim
69 words
A system as claimed in claim 1 wherein: each of said input terminals includes a keyboard which is actuable to input data to the system, said request means comprises a request key on said keyboard which is operative to initiate said request-for-service signal, and said lockout means is also operative to prevent input of a further request-for-service signal to the system before said proceed signal is received as aforesaid.
Claim 8
Dependent Claim
39 words
A system as claimed in claim 6 wherein said lockout means includes an electronic latch (herein called a request latch) which is activated by said request key and reset when said proceed signal is received at said remote station.
Claim 9
Dependent Claim
26 words
A system as claimed in claim 6 wherein: said lockout means includes means for preventing actuation of all keys on said keyboard except said request key.
Claim 10
Dependent Claim
47 words
A system as claimed in claim 8 wherein; said lockout means includes an electronic latch (herein called an enter latch) settable by said proceed signal, said means for preventing actuation being normally operative but being rendered inoperative when the enter latch is activated by the proceed signal.
Claim 11
Dependent Claim
39 words
A system as claimed in claim 9 wherein: said lockout means includes an electronic latch (herein called a request latch) which is activated by said request key and reset when said proceed signal is received at said remote station.
Claim 12
Dependent Claim
48 words
A system as claimed in claim 10 wherein: said enter latch is resettable by an end-of-message signal indicating that input of data from said input terminal has been completed at least temporarily, said means for preventing being rendered operative again upon resetting of the enter latch as aforesaid.
Claim 13
Dependent Claim
77 words
A system as claimed in claim 1 wherein: each of said remote stations includes at least one terminal and a control unit to which all the terminals at said remote station are connected in parallel; said control unit including a common interface with said transmission means which interface is shared by all terminals at said remote station, and being interconnected with the control units of the other remote stations by said transmission means in said series loop.
Claim 14
Dependent Claim
39 words
A system as claimed in claim 12 wherein each terminal at each remote station is an input terminal and includes a keyboard actuable to input data to the system, and said lockout means includes both mechanical and electronic elements.
Claim 15
Dependent Claim
67 words
A system as claimed in claim 13 wherein: said lockout means includes mechanical means at said terminal for preventing actuation of said keyboard and an electronic latch (herein called an enter latch) forming part of said control unit and activatable by said proceed signal; said mechanical means for preventing actuation being normally operative but being rendered inoperative when the enter latch is activated by the proceed signal.
Claim 16
Dependent Claim
53 words
A system as claimed in claim 14 wherein: the enter latch is resettable by an end-of-message signal indicating that input of data from said input terminal has been completed, at least temporarily, said mechanical means for preventing actuation of the keyboard being rendered operative again upon resetting of the enter latch as aforesaid.
Claim 17
Dependent Claim
196 words
A system as claimed in claim 13 wherein: said request means comprises a request key on said keyboard which is operative to initiate said request-for-service signal, and said lockout means is also operative to prevent input of a further request-for-service signal to the system before said proceed signal is received as aforesaid and includes mechanical means at said input terminal for preventing actuation of all keys on said keyboard except said request key, an electronic latch (herein called an enter latch) forming part of said control unit and activatable by said proceed signal, and another electronic latch (herein called a request latch) also forming part of said control unit; said request latch being activated by said request key and being reset when the proceed signal is received at said remote station; said mechanical means for preventing actuation being normally operative but being rendered inoperative when the enter latch is activated by the proceed signal; said enter latch being resettable by an end-of-message signal indicating that input of data from said input terminal has been completed, at least temporarily; said mechanical means for preventing actuation being rendered operative again upon resetting of the enter latch as aforesaid.
Claim 18
Dependent Claim
80 words
A system as claimed in claim 1 wherein the total number of terminals on said loop exceeds the number of terminals which can be assigned line positions for transmitting or receiving data at any one time, said system further comprising: queuing means at said central station operative to queue any terminal from which the central station has received a request-for-service signal until a line position becomes available for that terminal and the central station transmits a proceed signal to it.
Claim 19
Dependent Claim
24 words
A system as claimed in claim 17 wherein: said queuing means is operative to queue said terminals in accordance with a predetermined priority scheme.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-01-31 | 1975-08-02 | 1976-02-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-01-31 | 1979-08-02 | 1980-02-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-01-31 | 1983-08-02 | 1984-02-01 | $7700.00 | Window Closed / Lapsed |