US4040014A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Modem sharing device
Assignee: Unisys Corp
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Filing: 1976-09-13
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Granted: 1977-08-02
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Expires: 1996-09-13
Abstract
Abstract An electronic module including a logical interlock for interconnecting two data sources to a modem whereby only one of the two data sources is allowed to transmit data at a time. First and second flip-flops and logic gates controlled thereby are provided such that the first data source to present a Request-to-Send (RTS) signal is awarded priority and thereby selected to receive a Clear-to-Send (CTS) signal from the modem. A subsequent RTS signal from the non-selected data source is ineffective in establishing communication with such non-selected data source since that source is blocked from receiving a CTS signal from the modem. A clock signal is effectively employed to ensure that simultaneously-generated RTS signals from the two data sources are only responded to by one of the two data sources.
Inventors
- 👤 Arvin George Gehrking
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 15:43
CPC Classifications
H; H04; H04L; H04L5/00
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
182 words
In a communications system of the type including a plurality of line terminals for transmitting and receiving data to and from modem units, said line terminals and modems operating in response to Request-to-Send and Clear-to-Send commands, apparatus for sharing a single modem unit between plural line terminals comprising: a. a plurality of flip-flops individually associated with each of said line terminals; b. timing means responsive to a Request-to-Send signal from said line terminals for setting only one of said plurality of flip-flops at a time; c. means connecting the outputs of a given one of said plurality of flip-flops to the inputs of the remaining flip-flops such that so long as said given one of said plurality of flip-flops is set, the remaining flip-flops are prevented from being set; d. means connected to the outputs of said plurality of flip-flops for transmitting said Request-to-Send signal to said single modem; and e. means connected to said plurality of flip-flops for transmitting a Clear-to-Send signal from said single modem to only that line terminal associated with the set one of said plurality of flip-flops.
Claim 2
Dependent Claim
182 words
In a communications system of the type including a plurality of line terminals for transmitting and receiving data to and from modem units, said line terminals and modems operating in response to Request-to-Send and Clear-to-Send commands, apparatus for sharing a single modem unit between plural line terminals comprising: a. a plurality of flip-flops individually associated with each of said line terminals; b. timing means responsive to a Request-to-Send signal from said line terminals for setting only one of said plurality of flip-flops at a time; c. means connecting the outputs of a given one of said plurality of flip-flops to the inputs of the remaining flip-flops such that so long as said given one of said plurality of flip-flops is set, the remaining flip-flops are prevented from being set; d. means connected to the outputs of said plurality of flip-flops for transmitting said Request-to-Send signal to said single modem; and e. means connected to said plurality of flip-flops for transmitting a Clear-to-Send signal from said single modem to only that line terminal associated with the set one of said plurality of flip-flops.
Claim 3
Dependent Claim
34 words
Apparatus as in claim 1 and further including means for enabling the transmission of data between said single modem and only that line terminal associated with the set one of said plurality of flip-flops.
Claim 4
Dependent Claim
11 words
Apparatus as in claim 1 wherein said flip-flops are D-type flip-flops.
Claim 5
Dependent Claim
40 words
Apparatus as in claim 3 wherein said timing means comprises: a. a multiphase source of regularly occurring clock signals; and b. means connecting the individual phases of said multiphase clock source individually to the enable input of said D-type flip-flops.
Claim 6
Dependent Claim
230 words
In a communication system of the type including first and second line terminals for transmitting and receiving data to and from modem units, said line terminals and modems operating in response to Request-to-Send and Clear-to-Send commands, a modem sharing device disposed between a modem and said first and second line terminals, comprising in combination: a. a source of regularly occurring clock signals; b. a first bistable circuit coupled to said source and which is set by the first leading edge of a clock signal from said source following receipt of a Request-to-Send command from said first line terminal; c. a second bistable circuit coupled to said source and which is set by the first leading edge of a clock signal from said source following the receipt of a Request-to-Send command from said second line terminal; d. a first coincidence gate connected to said first bistable circuit for permitting transmission of a Clear-to-Send command from said modem to said first line terminal when said first bistable circuit is set; e. a second coincidence gate connected to said second bistable circuit for permitting transmission of a Clear-to-Send command from said modem to said second line terminal when said second bistable circuit is set; and d. interlock means connecting said first and second bistable cicuits for permitting only one of said first or second bistable circuits to be set at any given time.
Claim 7
Dependent Claim
230 words
In a communication system of the type including first and second line terminals for transmitting and receiving data to and from modem units, said line terminals and modems operating in response to Request-to-Send and Clear-to-Send commands, a modem sharing device disposed between a modem and said first and second line terminals, comprising in combination: a. a source of regularly occurring clock signals; b. a first bistable circuit coupled to said source and which is set by the first leading edge of a clock signal from said source following receipt of a Request-to-Send command from said first line terminal; c. a second bistable circuit coupled to said source and which is set by the first leading edge of a clock signal from said source following the receipt of a Request-to-Send command from said second line terminal; d. a first coincidence gate connected to said first bistable circuit for permitting transmission of a Clear-to-Send command from said modem to said first line terminal when said first bistable circuit is set; e. a second coincidence gate connected to said second bistable circuit for permitting transmission of a Clear-to-Send command from said modem to said second line terminal when said second bistable circuit is set; and d. interlock means connecting said first and second bistable cicuits for permitting only one of said first or second bistable circuits to be set at any given time.
References Cited (Backward Citations)
US3609693A
Cited
US3772656A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-08-01 | 1981-01-31 | 1981-08-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-08-01 | 1985-01-31 | 1985-08-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-08-01 | 1989-01-31 | 1989-08-02 | $7700.00 | Window Closed / Lapsed |