US 4,055,835 AGranted

Line-seizing apparatus

AssigneeManitou Systems, Inc.

InventorsDouglas R. Thornton, Jerome Smiglee

Life of this patent

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Abstract

Line-seizing circuitry is disclosed by which a plurality of remote terminals may be connected to a central data recorder over a single two-wire data line with only one terminal being in communication with the recorder at any one time. Tie-breaking circuitry is included to prevent two remote units from going onto the data line simultaneously. A current source is placed across the line and when any terminal goes on the line, a resistor is also placed across the line reducing the voltage thereon below a first voltage level; the other terminals sense that low voltage and are prevented from going on the line. Each terminal includes an oscillator and may go on line only during an output pulse of the oscillator. If two terminals should attempt to go on the line simultaneously, the voltage across the line is reduced below a second and lower voltage level, and both terminals are removed from the line. Each terminal then repeatedly attempts to go on line with every output pulse of its respective oscillator until the different frequencies of the separate oscillators causes one to go on the line a sufficient period of time prior to the second that the second is held off the line.

Claims11

Dependent claims

Line-seizing apparatus for establishing communication over a data line used in association with apparatus for generating an electric signal on the data line, said electric signal having a parameter with a nominal value when the data line is not in use, and comprising:

connecting means for coupling the line-seizing apparatus to the data line;
first parameter detection means coupled to said connecting means and generating a first electrical signal at an output when the parameter of the signal at said connecting means differs from the nominal value by an amount not exceeding a first predetermined amount;
second parameter detection means coupled to said terminal means and generating a second electrical signal at an output when the parameter of the signal at said connecting means differs from the nominal value by an amount not less than a second predetermined amount, said second predetermined amount being greater than said first predetermined amount;
first circuit means for repetitively generating a third electrical signal at an output;
second circuit means for generating a fourth electrical signal at an output when it is desired to seize the data line;
third circuit means for altering the impedance presented at said connecting means by the line-seizing apparatus in response to a fifth electrical signal at an input;
and
fourth circuit means coupled to said first parameter detection means output, said second parameter detection means output, said first circuit means output, said second circuit means output, and said third circuit means input for applying said fifth electrical signal to said third circuit means input in response to the simultaneous occurrence of said first, third, and fourth electrical signals and preventing said fifth electrical signal from being applied to said third circuit means input in response to the occurrence of said second electrical signal.

5 more elements

Line-seizing apparatus for establishing communication over a data line used in association with apparatus for generating an electric current through said data line and comprising:

connecting means for coupling the line-seizing apparatus to said data line;
first voltage detection means coupled to said connecting means and generating a first electrical signal at an output when the voltage across the connecting means is above a first voltage level;
second voltage detection means coupled to said connecting means and generating a second electrical signal at an output when the voltage across the connecting means is above a second voltage level, said second voltage level being less than said first voltage level;
first circuit means for repetitively generating a third electrical signal at an output;
second circuit means for generating a fourth electrical signal at an output when it is desired to seize the data line;
third circuit means for altering the impedance presented at said connecting means in response to a fifth electrical signal at an input;
and
fourth circuit means coupled to said first voltage detection means output, said second voltage detection means output, said first circuit means output, said second circuit means output, and said third circuit means input for applying said fifth electrical signal to said third circuit means input in response to the simultaneous occurrence of said first, third, and fourth electrical signals and preventing said fifth electrical signal from being applied to said third circuit means input in response to the occurrence of said second electrical signal.

5 more elements

Dependencies are inferred from the claim text.

Facts

Application: 05/702,001Filed 2 Jul 1976 · continuation
Priority: 18 Aug 1975
Granted: 25 Oct 1977
Term ends: Not estimatedThe source records don’t support an estimate.

Classification12 codes

G07F 7/08
Mechanisms actuated by objects other than coins to free or to actuate vending, hiring, coin or paper currency dispensing or refunding apparatus:…
G06F 7/62
Methods or arrangements for performing computations using a digital non-denominational number representation, i.e. number representation without…:…
G06F 13/376
With decentralised access control: using a contention resolving method, e.g. collision detection, collision avoidance
G06Q 20/4037
Solvency checks: remote solvency checks