US3919461A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Data transmission system
Assignee: TANKNOLOGY/ENGINEERED SYSTEMS Inc A CORP OF DE (DBA ENGINEERED SYSTEMS INC)
•
Filing: 1974-01-07
•
Granted: 1975-11-11
•
Expires: 1994-01-07
Abstract
Abstract In order to couple a plurality of data transmitting terminals to a data receiving device via a single transmission channel, the high side of the transmission line pair is biased through a resistor to the mark level such that an output transistor switch within each terminal disposed across the transmission line pair can force the space level by being switched to the ''''on'''' condition, thereby shorting the transmission line pair. At the inception of a contention period, all terminals are permitted to issue data to the line. However, any terminal attempting to place a mark on the line while any other terminal is placing a space will fail since the space is dominant. The marking terminal drops from contention, and the process continues until a single terminal remains active to complete its message transfer. Thereafter, another contention cycle is instituted and resolved.
Inventors
- 👤 Robert A Hunting
- 👤 Ness Bradford O Van
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 19:57
CPC Classifications
H; H04; H04L; H04L12/00; H04L12/28; H04L12/40; H04L12/407; H04L12/413; H04L12/4135; H04L5/00
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
106 words
In a data communication system comprising a plurality of data transmitting terminals coupled to a data receiving device via a single communication channel in a mark/space level format, the method of selecting a single one of the terminals for communicating a message to the data receiving device comprising the steps of: a. establishing simultaneous access by a plurality of the terminals to the communications channel; b. comparing, in each terminal, the level which that terminal attempts to impress on the communications channel and the actual level appearing on the communications channel; and c. aborting data transmission from each terminal in which a nocompare condition is detected.
Claim 2
Dependent Claim
106 words
In a data communication system comprising a plurality of data transmitting terminals coupled to a data receiving device via a single communication channel in a mark/space level format, the method of selecting a single one of the terminals for communicating a message to the data receiving device comprising the steps of: a. establishing simultaneous access by a plurality of the terminals to the communications channel; b. comparing, in each terminal, the level which that terminal attempts to impress on the communications channel and the actual level appearing on the communications channel; and c. aborting data transmission from each terminal in which a nocompare condition is detected.
Claim 3
Dependent Claim
41 words
The method of claim 1 which includes the step of establishing a dominant level which the communications channel will accept from one or more terminals independent of simultaneous attempts by one or more additional terminals to impress the other level thereon.
Claim 4
Dependent Claim
14 words
The method of claim 2 in which the dominant level is nominally zero volts.
Claim 5
Dependent Claim
24 words
The method of claim 3 in which any terminal may issue a dominant level by effectively shorting a line pair constituting the transmission channel.
Claim 6
Dependent Claim
140 words
Apparatus for controlling data communication to a data receiving device from a plurality of data terminals via a single line pair communications channel in a mark/space level format, comprising: a. means for biasing a first line of said line pair to a first level; b. means for clamping a second line of said line pair to a second level; c. switch means in each of said terminals electrically disposed across said line pair such that closure of any one or more switches forces said first line to said second level; d. comparator means in each of said terminals for comparing the state of said switch means in that said terminal to the level on said first line; and e. abort means in each of said terminals responsive to said comparator means for disabling that said terminal from further data transmission.
Claim 7
Dependent Claim
140 words
Apparatus for controlling data communication to a data receiving device from a plurality of data terminals via a single line pair communications channel in a mark/space level format, comprising: a. means for biasing a first line of said line pair to a first level; b. means for clamping a second line of said line pair to a second level; c. switch means in each of said terminals electrically disposed across said line pair such that closure of any one or more switches forces said first line to said second level; d. comparator means in each of said terminals for comparing the state of said switch means in that said terminal to the level on said first line; and e. abort means in each of said terminals responsive to said comparator means for disabling that said terminal from further data transmission.
Claim 8
Dependent Claim
42 words
The apparatus of claim 5 which further includes line sensor means in each of said terminals, said line sensor means being responsive to said first line remaining at said first level for a predetermined period by eNabling said terminal to transmit data.
Claim 9
Dependent Claim
39 words
The apparatus of claim 6 in which each of said switch means comprises an output transistor adapted to be switched between on and off states to, respectively, short said line pair and have no effect on said line pair.
Claim 10
Dependent Claim
44 words
The apparatus of claim 7 in which said biasing means comprises a resistor connected between a voltage source and said first line whereby the full voltage from said source is dropped across said resistor when at least one of said output transistors is on.
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) | 1978-11-10 | 1979-05-12 | 1979-11-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-11-10 | 1983-05-12 | 1983-11-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-11-10 | 1987-05-12 | 1987-11-11 | $7700.00 | Window Closed / Lapsed |