Switch sensing emergency lighting device

1. A lighting unit comprising:

a power input adapted to receive power via a power supply circuit, wherein the power supply circuit is adapted to receive a supply of power from a primary power source through a switch and includes a secondary source of power;

at least one light source adapted to receive power via the power input;

a sensor configured to generate an output indicative of a reflected signal arising from application of an electrical signal; and

a controller configured to:

cause application of the electrical signal to the power supply circuit;

determine an operational state of the switch based on a comparison of one or more measurements of the output of the sensor with a threshold; and

cause the power from the secondary source of power to be supplied to the light source when power from the primary source is not present on the power input and the determined operational state of the switch indicates that the switch is in a closed state.

2. The lighting unit of claim 1 , wherein the threshold is set manually.

3. The lighting unit of claim 1 , wherein establishing the threshold level further includes dynamically setting the threshold value according to at least one measurement relating to the operational state of the switch.

4. The lighting unit of claim 1 , wherein the applied electrical signal is a short rise time pulse and the sensor generates the output indicative of a time domain reflectometry process involving the short rise time pulse.

5. The lighting unit of claim 1 , wherein the secondary source of power is integrated into the lighting unit.

6. The lighting unit of claim 1 , wherein the secondary source of power includes at least one of a rechargeable battery, a non-rechargeable battery, a photovoltaic cell, fuel cell, or super capacitor.

7. The lighting unit of claim 6 , wherein the controller is further configured to control charging of the at least one rechargeable battery, fuel cell, or super capacitor.

8. The lighting unit of claim 6 , wherein the photovoltaic cell is configured to recharge the at least one rechargeable battery, fuel cell, or super capacitor.

9. The lighting unit of claim 1 , wherein the lighting unit is configured for mounting to an Edison socket.

10. The lighting unit of claim 1 , further including a timer, wherein the controller is further configured to control a supply of power to the light source based at least in part on an output of the timer.

11. The lighting unit of claim 1 , further including an environmental sensor and wherein the controller is further configured to control a supply of power to the light source based at least in part on an output of the environmental sensor.

12. The lighting unit of claim 1 , wherein the controller is further configured to turn the light source on or off, change an illumination level of the light source, flash the light source, or change a color content of illumination of the light source.

13. The lighting unit of claim 1 , wherein the switch includes a dimmer switch.

14. The lighting unit of claim 1 , wherein the lighting unit comprises a bulb, tube, lamp, lighting fixture, or retrofit fixture.

15. The lighting unit of claim 1 , wherein the controller is further configured to change at least an illumination level of the light source to increase the energy efficiency of the lighting unit and wherein increasing the energy efficiency of the lighting unit includes decreasing power supplied from the secondary source of power supplied to the light source.

16. A retrofit lighting fixture comprising:

a housing configured for installation into an existing structure;

a power input adapted to receive power via a power supply circuit associated with the existing structure, wherein the power supply circuit receives a power from a primary power source through a switch;

at least one light source adapted to receive power via the power input;

a source of secondary source of power adapted to selectively provide power to the at least one light source;

a sensor configured to generate an output indicative of a reflected signal arising from application of an electrical signal; and

a controller configured to:

cause application of the electrical signal to the power supply circuit;

make at least one determination of an operational state of the switch based on a comparison of one or more measurements of the output of the sensor and a threshold; and

cause power from the secondary source of power to be supplied to the at least one light source from the secondary source of power when power through the switch is not present on the power input and the operational state of the switch indicates that the switch is in a closed state.

17. The lighting unit of claim 16 , wherein the threshold is set one of manually or dynamically.

18. The lighting unit of claim 16 wherein:

the secondary source of power is integrated into the lighting unit and includes at least one of a rechargeable battery, a non-rechargeable battery, a photovoltaic cell, fuel cell, or super capacitor.

19. A lighting fixture comprising:

an adapter for connecting the lighting fixture to a connector;

a power input configured to receive power via a power supply circuit from a primary source of power, the power supply circuit comprising a switch;

at least one light source adapted to receive power via the power input;

a secondary source of power adapted to provide power to the at least one light source;

a sensor configured to generate an output indicative of a reflected signal arising from application of an electrical signal; and

a controller configured to:

cause application of the electrical signal to the power supply circuit; and

cause power from the secondary source to be supplied to the at least one light source when power from the primary source is not present on the power input and when one or more measurements of the sensor output by the controller indicates that the switch is in a closed operational state.

20. The lighting fixture of claim 19 wherein the adapter comprises a plurality of wires.

21. A lighting unit comprising:

a power input adapted to receive power via a power supply circuit, wherein the power supply circuit is adapted to receive a supply of power from a primary power source through a switch and includes a secondary source of power;

at least one light source adapted to receive power via the power input;

a sensor configured to generate an output indicative of an effect of an operational state of the switch on an electrical signal applied to the power supply circuit; and

a controller configured to:

cause application of the electrical signal to the power supply circuit;

determine an operational state of the switch based on a comparison of the output of the sensor with a threshold, the threshold relating to the effect of the operational state of the switch on the electrical signal applied to the power supply circuit; and

cause the power from the secondary source of power to be supplied to the light source when power from the primary source is not present on the power input and the determined operational state of the switch indicates that the switch is in a closed state.

22. A lighting unit comprising:

a power input adapted to receive power via a power supply circuit, wherein the power supply circuit is adapted to receive a supply of power from a primary power source through a switch and includes a secondary source of power;

at least one light source adapted to receive power via the power input;

a sensor configured to generate an output indicative of an electrical response associated with the power supply circuit; and

a controller configured to:

cause application of an electrical signal to the power supply circuit;

determine an operational state of the switch based on a comparison of one or more measurements of the output of the sensor with a threshold, the threshold relating to the presence of an impedance discontinuity in the power supply circuit and

cause the power from the secondary source of power to be supplied to the light source when power from the primary source is not present on the power input and the determined operational state of the switch indicates that the switch is in a closed state.