US3673467A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Resistively-coded security system
Assignee: Eaton Corp
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Filing: 1970-10-28
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Granted: 1972-06-27
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Expires: 1990-10-28
Abstract
Abstract An electronic key-actuated security system including keys each constituted by a plurality of electrically resistive elements. Key-receiving means includes conductors which provide connections with resistive elements of a key received. The system includes a plurality of bridges each associated with one of the resistive elements of a key received. Each of said bridges has first, second and third impedance arms, a respective one of the key resistive elements being connected as a fourth impedance arm of each said bridge. The first and second arms define a first preset impedance ration, and the third and fourth arms define a second impedance ration, the bridge being electrically balanced when these ratios are equal. Logic gate means is interconnected with each of the bridges and supplies an output signal when all of the bridges are balanced. Electrically actuatable means, e.g., a latch, is responsive to this output signal for indicating thereby the receiving of a key having resistive elements causing balancing of all the bridges. A key for use with the system includes a nonconductive portion adapted to be inserted in the key-receiving means. Pairs of contacts are bilaterally symmetrical with respect to an axis of symmetry extending in the direction of insertion of the key with the result that the key is adapted for bilateral insertion.
Inventors
- 👤 William Eisenreich
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 15:15
CPC Classifications
G; G07; G07C; G07C9/00; G07C9/00174; G07C9/00658; G07C9/00714; G07C9/20
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
310 words
Apparatus for use in an electronic key-actuated security system including keys each constituted by a plurality of electrically resistive elements, said apparatus comprising: key-receiving means including conductors for providing connections with resistive elements of a key received; a plurality of bridges, each associated with a resistive element of a key received, each of said bridges including first, second and third impedance arms, said key-receiving means being adapted to connect a respective one of said resistive elements as a fourth impedance arm of each of said bridges, said first and second impedance arms defining a first preset impedance ratio, said third and fourth impedance arms defining a second impedance ratio, each of said bridges having first and second output terminals having a potential thereon with the potential developed at said first terminal being indicative of the first preset impedance ratio and the potential developed at said second terminal being indicative of said second impedance ratio, each of said bridges being adapted to be electrically balanced to apply equal potentials to said first and second output terminals when said impedance ratios are equal; a plurality of differential amplifiers, each associated with one of said bridge circuits, and each having an output which is a function of said impedance ratios; logic gate means interconnected with said differential amplifiers and responsive to an output signal of said differential amplifier which is indicative of predetermined ratios being developed between the potentials on said first and second output terminals of each of said bridges for supplying an output signal only when the potentials developed on said first and second output terminals of each of said bridges form said predetermined ratios; and electrically actuatable means responsive to said output signal for indicating thereby the receiving of a key having resistive elements of respective resistance values causing said predetermined ratios to be developed on all of said bridges.
Claim 2
Dependent Claim
310 words
Apparatus for use in an electronic key-actuated security system including keys each constituted by a plurality of electrically resistive elements, said apparatus comprising: key-receiving means including conductors for providing connections with resistive elements of a key received; a plurality of bridges, each associated with a resistive element of a key received, each of said bridges including first, second and third impedance arms, said key-receiving means being adapted to connect a respective one of said resistive elements as a fourth impedance arm of each of said bridges, said first and second impedance arms defining a first preset impedance ratio, said third and fourth impedance arms defining a second impedance ratio, each of said bridges having first and second output terminals having a potential thereon with the potential developed at said first terminal being indicative of the first preset impedance ratio and the potential developed at said second terminal being indicative of said second impedance ratio, each of said bridges being adapted to be electrically balanced to apply equal potentials to said first and second output terminals when said impedance ratios are equal; a plurality of differential amplifiers, each associated with one of said bridge circuits, and each having an output which is a function of said impedance ratios; logic gate means interconnected with said differential amplifiers and responsive to an output signal of said differential amplifier which is indicative of predetermined ratios being developed between the potentials on said first and second output terminals of each of said bridges for supplying an output signal only when the potentials developed on said first and second output terminals of each of said bridges form said predetermined ratios; and electrically actuatable means responsive to said output signal for indicating thereby the receiving of a key having resistive elements of respective resistance values causing said predetermined ratios to be developed on all of said bridges.
Claim 3
Dependent Claim
74 words
Apparatus as set forth in claim 1 wherein said logic gate means comprises a plurality of AND gates each associated with one of said bridges and each connected for providing an intermediate signal in response to balancing of the associated bridge, and a further AND gate interconnected with each of the first-said AND gatEs and adapted to supply the first-said output signal in response to intermediate signals from each of the first-said AND gates.
Claim 4
Dependent Claim
249 words
Apparatus for use in an electronic key-actuated security system including keys each constituted by a plurality of electrically resistive elements, said apparatus comprising: key-receiving means including conductors for providing connections with resistive elements of a key received; a plurality of bridge circuits, each associated with a resistive element of a key received, each of said bridge circuits including first, second and third impedance arms, said key-receiving means being adapted to connect a respective one of said resistive elements as a fourth impedance arm of each of said bridge circuits, said first and second impedance arms defining a first preset impedance ratio, said third and fourth impedance arms defining a second impedance ratio, each of said bridge circuits being adapted to be electrically balanced when said ratios are equal; a plurality of differential amplifiers, each associated with one of said bridge circuits, and each having an output which is a function of said ratios; logic gate means responsive to the outputs of said differential amplifiers for supplying an output signal when said ratios are equal for each of said bridge circuits; each of said differential amplifiers including a pair of inputs connected across a respective one of said bridge circuits and a pair of differential outputs connected to a respective pair of inputs of said logic gate means; and electrically actuatable means responsive to said output signal for indicating thereby the receiving of a key having resistive elements of respective resistance values causing balancing of all of said bridge circuits.
Claim 5
Dependent Claim
249 words
Apparatus for use in an electronic key-actuated security system including keys each constituted by a plurality of electrically resistive elements, said apparatus comprising: key-receiving means including conductors for providing connections with resistive elements of a key received; a plurality of bridge circuits, each associated with a resistive element of a key received, each of said bridge circuits including first, second and third impedance arms, said key-receiving means being adapted to connect a respective one of said resistive elements as a fourth impedance arm of each of said bridge circuits, said first and second impedance arms defining a first preset impedance ratio, said third and fourth impedance arms defining a second impedance ratio, each of said bridge circuits being adapted to be electrically balanced when said ratios are equal; a plurality of differential amplifiers, each associated with one of said bridge circuits, and each having an output which is a function of said ratios; logic gate means responsive to the outputs of said differential amplifiers for supplying an output signal when said ratios are equal for each of said bridge circuits; each of said differential amplifiers including a pair of inputs connected across a respective one of said bridge circuits and a pair of differential outputs connected to a respective pair of inputs of said logic gate means; and electrically actuatable means responsive to said output signal for indicating thereby the receiving of a key having resistive elements of respective resistance values causing balancing of all of said bridge circuits.
Claim 6
Dependent Claim
314 words
Apparatus for use in an electronic key-actuated security system including keys each constituted by a plurality of electrically resistive elements, said apparatus comprising: key-receiving means including conductors for providing connections with resistive elements of a key received; a plurality of bridge circuits, each associated with a resistive element of a key received, each of said bridge circuits including first, second and third impedance arms, said key-receiving means being adapted to connect a respective one of said resistive elements as a fourth impedance arm of each of said bridge circuits, said first and second impedance arms defining a first preset impedance ratio, said third and fourth impedance arms defining a second impedance ratio, each of said bridge circuits being adapted to be electrically balanced when said ratios are equal; a plurality of differential input voltage comparators, each associated with one of said bridge circuits, and each having an output which is a function of said ratios; logic gate means responsive to the outputs of said voltage comparators for supplying an output signal when said ratios are equal for each of said bridge circuits; electrically actuatable means responsive to said output signal for indicating thereby the receiving of a key having resistive elements of respective resistance values causing balancing of all of said bridge circuits; and said logic gate means comprising a plurality of AND gates each associated with one of said bridge circuits and each having a pair of inputs connected for being supplied with input potentials of preselected equal level in response to balancing of the associated bridge circuit to cause the AND gate to provide a potential at the output thereof, and a further AND gate having input terminals interconnected with the outputs of each of the first-said AND gates, the output of said further AND gates supplying said output signal when each of the first-said AND gates provides a respective output potential.
Claim 7
Dependent Claim
314 words
Apparatus for use in an electronic key-actuated security system including keys each constituted by a plurality of electrically resistive elements, said apparatus comprising: key-receiving means including conductors for providing connections with resistive elements of a key received; a plurality of bridge circuits, each associated with a resistive element of a key received, each of said bridge circuits including first, second and third impedance arms, said key-receiving means being adapted to connect a respective one of said resistive elements as a fourth impedance arm of each of said bridge circuits, said first and second impedance arms defining a first preset impedance ratio, said third and fourth impedance arms defining a second impedance ratio, each of said bridge circuits being adapted to be electrically balanced when said ratios are equal; a plurality of differential input voltage comparators, each associated with one of said bridge circuits, and each having an output which is a function of said ratios; logic gate means responsive to the outputs of said voltage comparators for supplying an output signal when said ratios are equal for each of said bridge circuits; electrically actuatable means responsive to said output signal for indicating thereby the receiving of a key having resistive elements of respective resistance values causing balancing of all of said bridge circuits; and said logic gate means comprising a plurality of AND gates each associated with one of said bridge circuits and each having a pair of inputs connected for being supplied with input potentials of preselected equal level in response to balancing of the associated bridge circuit to cause the AND gate to provide a potential at the output thereof, and a further AND gate having input terminals interconnected with the outputs of each of the first-said AND gates, the output of said further AND gates supplying said output signal when each of the first-said AND gates provides a respective output potential.
Claim 8
Dependent Claim
50 words
Apparatus as set forth in claim 4 further comprising a plurality of voltage comparators each having a pair of differential inputs connected across a respective one of said bridge circuits and a pair of differential outputs connected to a respective pair of inputs of one of the first-said AND gates.
Claim 9
Dependent Claim
38 words
Apparatus as set forth in claim 5 wherein said electrically actuatable means comprises an electric latch and a triggerable semiconductor switching device interconnected for energizing said latch when triggered, said output signal causing triggering of said switching device.
Claim 10
Dependent Claim
56 words
Apparatus as set forth in claim 6 including an alarm signalling device, time delay means operative in response to receiving of a key for energizing said signalling device after a predetermined time delay period following the receiving of the key, and means operative in response to said output signal for preventing energization of said signalling device.
Claim 11
Dependent Claim
101 words
Apparatus as set forth in claim 7 including a logic OR gate having a plurality of inputs each interconnected with one of said voltage comparators, and wherein said means for preventing energization comprises a still further AND gate having one input terminal interconnected with the output terminal of said OR gate, another input terminal adapted to be supplied with a potential in the absence of said output signal, and an output terminal connected for causing energization of said time delay means, said output signal thereby preventing energization of said time delay means so as to prevent energization of said signalling means.
Claim 12
Dependent Claim
262 words
Apparatus for use in a key-actuated security system including keys each constituted by a plurality of electrically resistive elements, said apparatus comprising: key-receiving means including conductors for providing connections with resistive elements of a key received; a plurality of voltage dividers, each including a preset impedance and each adapted to have a resistive element of a received key interconnected with said preset impedance by said key-receiving means and with a voltage source to provide a first potential whose level is a function of said impedance and the resistance value of the interconnected respective element; means for supplying a reference potential; a plurality of voltage comparators, each associated with one of said voltage dividers and each having a pair of differential input terminals and a pair of differential output terminals, the potentials at the output terminals of each comparator being of predetermined equal levels when the levels of potentials applied to the input terminals thereof have a predetermined relationship; circuit means for applying said first potential provided by each voltage divider to one of said input terminals of the respective comparator and applying said reference potential to the other of said comparator input terminals; logic gate means, including an AND gate, connected to each of said output terminals and providing an output signal when the potentials at each pair of said comparator output terminals are each of said predetermined equal levels; and electrically actuatable means responsive to the output signal from said logic gate means for indicating thereby the receiving of a key having resistive elements of resistance values producing said predetermined relationship.
Claim 13
Dependent Claim
262 words
Apparatus for use in a key-actuated security system including keys each constituted by a plurality of electrically resistive elements, said apparatus comprising: key-receiving means including conductors for providing connections with resistive elements of a key received; a plurality of voltage dividers, each including a preset impedance and each adapted to have a resistive element of a received key interconnected with said preset impedance by said key-receiving means and with a voltage source to provide a first potential whose level is a function of said impedance and the resistance value of the interconnected respective element; means for supplying a reference potential; a plurality of voltage comparators, each associated with one of said voltage dividers and each having a pair of differential input terminals and a pair of differential output terminals, the potentials at the output terminals of each comparator being of predetermined equal levels when the levels of potentials applied to the input terminals thereof have a predetermined relationship; circuit means for applying said first potential provided by each voltage divider to one of said input terminals of the respective comparator and applying said reference potential to the other of said comparator input terminals; logic gate means, including an AND gate, connected to each of said output terminals and providing an output signal when the potentials at each pair of said comparator output terminals are each of said predetermined equal levels; and electrically actuatable means responsive to the output signal from said logic gate means for indicating thereby the receiving of a key having resistive elements of resistance values producing said predetermined relationship.
Claim 14
Dependent Claim
224 words
A key-actuated security system comprising: a key including a plurality of electrically resistive elements, each of a preselected resistance value; means for receiving said key including conductors for providing connections with resistive elements of said key; a plurality of circuit means each associated with a resistive element of said key, each of the circuit means including a preset impedance and each adapted to have the associated resistive element of said key interconnected with said preset impedance by the key-receiving means, each of the circuit means providing a first potential whose level is a function of said preset impedance and the resistance value of the interconnected resistive element; means for supplying a reference potential; a plurality of voltage comparators each associated witH one of said circuit means and each responsive to said first and reference potentials, each of said comparators including output terminals providing potentials which are of predetermined equal level when said first and reference potentials have a predetermined relationship; logic gate means interconnected with the output terminals of each of said comparing means and providing an output signal when the output potentials at each pair of output terminals are each of said predetermined equal level; and electrically actuatable means responsive to said output signal for indicating thereby that said key when received has resistive elements of preselected resistance values producing said predetermined relationship.
Claim 15
Dependent Claim
224 words
A key-actuated security system comprising: a key including a plurality of electrically resistive elements, each of a preselected resistance value; means for receiving said key including conductors for providing connections with resistive elements of said key; a plurality of circuit means each associated with a resistive element of said key, each of the circuit means including a preset impedance and each adapted to have the associated resistive element of said key interconnected with said preset impedance by the key-receiving means, each of the circuit means providing a first potential whose level is a function of said preset impedance and the resistance value of the interconnected resistive element; means for supplying a reference potential; a plurality of voltage comparators each associated witH one of said circuit means and each responsive to said first and reference potentials, each of said comparators including output terminals providing potentials which are of predetermined equal level when said first and reference potentials have a predetermined relationship; logic gate means interconnected with the output terminals of each of said comparing means and providing an output signal when the output potentials at each pair of output terminals are each of said predetermined equal level; and electrically actuatable means responsive to said output signal for indicating thereby that said key when received has resistive elements of preselected resistance values producing said predetermined relationship.
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) | 1975-06-27 | 1975-12-27 | 1976-06-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-06-27 | 1979-12-27 | 1980-06-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-06-27 | 1983-12-27 | 1984-06-27 | $7700.00 | Window Closed / Lapsed |