Alarm systems and devices incorporating current limiting circuit
First Claim
1. A condition responsive impedance altering circuit comprising:
- first and second terminals;
a first impedance branch coupled between the terminals;
a second, variable, impedance branch coupled between the terminals; and
control circuitry coupled to at least the second branch wherein the control circuitry varies the impedance of the second branch between a first, relatively high, impedance value and a second relatively low, impedance value in response to a selected condition wherein the control circuitry includes a timing element and in response to a predetermined elapsed time varies the impedance of the second branch.
1 Assignment
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Accused Products
Abstract
Electrical modules which incorporate multiple state input circuitry limit the in-rush current thereto when electrical energy is initially applied. The input circuitry exhibits a high impedance and subsequently a very low impedance state. When electrical energy is first applied, the high impedance state limits the in-rush current to an acceptable predetermined maximum value. Subsequently, in response to either elapsed time or an electrical parameter such as current flow, the circuit switches to a low impedance state which results in its having no material effect on the operation of the module. The module can incorporate a visual alarm indicating output device, an audible alarm indicating output device or both. The output indicating devices can be synchronized by applied control signals. The output devices can be controlled independently by means of either pulse width modulated control signals or by means of patterns of control pulses.
34 Citations
33 Claims
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1. A condition responsive impedance altering circuit comprising:
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first and second terminals; a first impedance branch coupled between the terminals; a second, variable, impedance branch coupled between the terminals; and control circuitry coupled to at least the second branch wherein the control circuitry varies the impedance of the second branch between a first, relatively high, impedance value and a second relatively low, impedance value in response to a selected condition wherein the control circuitry includes a timing element and in response to a predetermined elapsed time varies the impedance of the second branch. - View Dependent Claims (2, 3, 4)
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5. A module with a predetermined turn-on electrical current comprising:
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a load; a control element coupled to the load; a multi-state impedance altering circuit coupled at least to the load and the control element wherein when electrical energy is first applied to the module, the circuit exhibits a first impedance thereby limiting the turn-on current to a predetermined maximum value and wherein after a preset time interval the circuit exhibits a second impedance. - View Dependent Claims (6, 7, 8, 9)
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10. A condition responsive input impedance altering circuit couplable to an input port of an electrical unit comprising:
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first and second terminals wherein one of the terminals is couplable to the input port; a controllable, variable impedance circuit coupled between the terminals wherein the circuit includes a control port and exhibits first and second impedances value in response to signals applied to the control port; a programmable control element coupled to the control port wherein in response to the application of electrical energy to the unit, the control element applies a first control signal to the control port thereby causing the variable impedance circuit to exhibit the first impedance and in response to detection of an elapsed time interval subsequent to the application for electrical energy, the control element applies a second control signal to the control port thereby causing the variable impedance circuit to exhibit the second impedance. - View Dependent Claims (11, 12, 13, 14, 15)
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16. An ambient condition monitoring system comprising:
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a control element; a power supplying communications link coupled to the control element; at least one alarm indicating output device coupled to the link wherein the output device includes multiple state peak current limiting circuitry and wherein the output device includes circuitry which responds to one of received pulse width modulated control signals and received pulse position modulated control signals. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23)
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24. An alarm output device comprising:
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a visual output device; a control circuit coupled to the output device; a variable impedance turn-on current limiting circuit coupled to the control circuit wherein the current limiting circuit is adapted to switch from a first impedance state to a second impedance state in response to an elapsed time interval. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31)
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32. An output device to be switched from an inactive state to an active state in response to switching the polarity of an applied input voltage comprising:
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a timing circuit, responsive to switching the polarity for timing out the duration of a preselected time interval; a multi-state impedance network with a control port coupled to the timing circuit, an input port for receiving applied input voltage and an output port; and an output transducer coupled to the output port and including circuitry for responding to pulse modulated control signals. - View Dependent Claims (33)
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Specification