Patent US3908086A successfully refreshed from Google Patents.
US3908086A
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Method for establishing a data communication connection between two full duplex modems
Assignee: REDACTRON CORP
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Filing: 1974-06-03
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Granted: 1975-09-23
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Expires: 1994-06-03
Abstract
Abstract When two full duplex modems are connected via a telephone network and a call is made from one modem to the other ringing energy causes the application of power to the called modem which is energized to operate randomly in either the originating or answering mode. If the called modem does not detect the receipt of carrier signal from the calling modem within a given time interval, the called modem switches operating modes and again attempts to detect the receipt of carrier signals. Whenever carrier signal is detected the modem locks in the then present mode and data communication can begin.
Inventors
- 👤 Francis C Marino
- 👤 Edward Krummenacker
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 10:39
CPC Classifications
H; H04; H04M; H04M11/00; H04M11/06
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
243 words
In a data communication system wherein at least a pair of full duplex modems are connected together by a telecommunication system to communicate through the transfer of frequency shift keyed carrier signals and wherein at least one of the modems is initially unpowered, a method of establishing a data communications connection between the modems by forcing the condition that one of the modems operates in an originating operating mode with a first frequency band and the other modem operates in an answering operating mode with a second frequency band, said method comprising the steps of a first of the modems in one of the operating modes calling a second of the modems, the second modem being unpowered, applying power to the second modem in response to the call of the first modem, forcing the second modem into an arbitrary one of the operating modes, the first modem transmitting carrier signals in the frequency band associated with its present operating mode, the second modem sensing for the receipt of such carrier signals from the first modem, if such carrier signals are sensed within a predetermined time activating data transfer routines between the two modems, if such carrier signals are not sensed within the predetermined time forcing the second modem to switch to the other operating mode and to again sense for the receipt of such carrier signals, and when such carrier signals are then sensed by the second modem activating the data transfer routines.
Claim 2
Dependent Claim
243 words
In a data communication system wherein at least a pair of full duplex modems are connected together by a telecommunication system to communicate through the transfer of frequency shift keyed carrier signals and wherein at least one of the modems is initially unpowered, a method of establishing a data communications connection between the modems by forcing the condition that one of the modems operates in an originating operating mode with a first frequency band and the other modem operates in an answering operating mode with a second frequency band, said method comprising the steps of a first of the modems in one of the operating modes calling a second of the modems, the second modem being unpowered, applying power to the second modem in response to the call of the first modem, forcing the second modem into an arbitrary one of the operating modes, the first modem transmitting carrier signals in the frequency band associated with its present operating mode, the second modem sensing for the receipt of such carrier signals from the first modem, if such carrier signals are sensed within a predetermined time activating data transfer routines between the two modems, if such carrier signals are not sensed within the predetermined time forcing the second modem to switch to the other operating mode and to again sense for the receipt of such carrier signals, and when such carrier signals are then sensed by the second modem activating the data transfer routines.
Claim 3
Dependent Claim
22 words
The method of claim 1 wherein the second modem is turned on in response to a ringing signal from the first modem.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-09-22 | 1979-03-24 | 1979-09-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-09-22 | 1983-03-24 | 1983-09-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-09-22 | 1987-03-24 | 1987-09-23 | $7700.00 | Window Closed / Lapsed |