Failure detection circuit

Claim 2

A circuit for detecting the electrical failure of any of a plurality of electrical devices each of which requires a predetermined current to operate comprising, in combination, a plurality of resistors, means connecting a different one of said resistors in series with each of the devices, means for causing currents less than the predetermined currents to flow through the devices, the current through any device decreasing to below such lesser currents in the event of a failure of such device, said current causing means causing currents to flow through each series resistor and device when such device is not operating, a plurality of switch means for selectively shorting each of said resistors for selectively increasing the current in each device to the predetermined operating current, an alarm, and switch means for energizing said alarm in response to such a decrease in the current through any of the devices.

Claim 3

A circuit for detecting the electrical failure of any of a plurality of electrical devices each of which requires a predetermined current to operate comprising, in combination, a plurality of resistors, means connecting a different one of said resistors in series with each of the devices, means for causing currents less than the predetermined currents to flow through the devices, the current through any device decreasing to below such lesser currents in the event of a failure of such device, said current causing means causing currents to flow through each series resistor and device when such device is not operating, a plurality of switch means for selectively shorting each of said resistors for selectively increasing the current in each device to the predetermined operating current, an alarm, and switch means for energizing said alarm in response to such a decrease in the current through any of the devices.

Claim 4

A circuit for detecting the electrical failure of any of a plurality of electrical devices each of which requires a predetermined current to operate comprising, in combination, a plurality of resistors, means connecting a different one of said resistors in series with each of the devices, means for causing currents less than the predetermined currents to flow through the devices, the current through any device decreasing to below such lesser currents in the event of a failure of such device, said current causing means causing currents to flow through each series resistor and device when such device is not operating, a plurality of switch means for selectively shorting each of said resistors for selectively increasing the current in each device to the predetermined operating current, an alarm, and switch means for energizing said alarm in response to such a decrease in the current through any of the devices.

Claim 5

A circuit for detecting the electrical failure of any of a plurality of electrical devices each of which requires a predetermined current to operate comprising, in combination, means for causing cUrrents less than the predetermined operating currents to flow through the devices, the current through any device decreasing to below such lesser currents in the event of a failure of such device, an alarm, first switch means for energizing said alarm in response to such a decrease in the current through any of the devices, a plurality of second switch means, each of said second switch means having a predetermined voltage drop when closed, means connecting a different one of said second switch means in series with each of the devices for selectively energizing the devices, and means connecting the junctions between each of the devices and the connected second switch means to said first switch means for energizing said alarm.

Claim 6

A circuit for detecting the electrical failure of any of a plurality of electrical devices each of which requires a predetermined current to operate comprising, in combination, means for causing cUrrents less than the predetermined operating currents to flow through the devices, the current through any device decreasing to below such lesser currents in the event of a failure of such device, an alarm, first switch means for energizing said alarm in response to such a decrease in the current through any of the devices, a plurality of second switch means, each of said second switch means having a predetermined voltage drop when closed, means connecting a different one of said second switch means in series with each of the devices for selectively energizing the devices, and means connecting the junctions between each of the devices and the connected second switch means to said first switch means for energizing said alarm.

Claim 7

In combination with a plurality of electrical devices, a circuit for detecting the failure of any of said devices comprising a power source, a plurality of resistors, each of said resistors connecting a different one of said devices to said source whereby a predetermined low current flows through each good device, said low current in each device being lower than the current required to energize such device, means including a plurality of isolation diodes for connecting the junctions between said resistors and said devices to a common terminal whereby a first voltage appears on said terminal when all of said devices are good and a second voltage appears on said terminal upon the failure of any of said devices, an alarm, and switch means connected to said terminal and responsive to a change from said first voltage to said second voltage for energizing said alarm.

Claim 8

In combination with a plurality of electrical devices, a circuit for detecting the failure of any of said devices comprising a power source, a plurality of resistors, each of said resistors connecting a different one of said devices to said source whereby a predetermined low current flows through each good device, said low current in each device being lower than the current required to energize such device, means including a plurality of isolation diodes for connecting the junctions between said resistors and said devices to a common terminal whereby a first voltage appears on said terminal when all of said devices are good and a second voltage appears on said terminal upon the failure of any of said devices, an alarm, and switch means connected to said terminal and responsive to a change from said first voltage to said second voltage for energizing said alarm.

Claim 9

The combination of claim 3, wherein said switch means comprises a first transistor having a control electrode connected to said terminal, means for biasing said first transistor into a conducting state when the first voltage is applied to said control electrode and into a nonconducting state when the second voltage is applied to said control electrode, and a second transistor having an input connected to said first transistor and an output connected to said alarm, said second transistor conducting to energize said alarm when said first transistor is nonconducting.

Claim 10

The combination of claim 3 and including means for selectively energizing each of said devices.

Claim 11

The combination of claim 5, wherein said means for selectively energizing each of said devices includes a plurality of current limiting resistors, means connecting a different one of said current limiting resistors in series with each of said devices, a plurality of switches, and means connecting a different one of said switches in parallel with each of said current limiting resistors whereby the closure of each switch energizes a different one of said devices.

Claim 12

The combination of claim 4, wherein said devices are incandescent lamps.

Claim 13

In combination with a plurality of electrical devices, a circuit for detecting the failure of any of said devices comprising a power source, a plurality of first switch means, a predetermined current flowing through each of said first switch means when closed, means connecting each of said devices and a different one of said first switch means in series, means connecting all of said series connected devices and first switch means in parallel to said power source whereby said devices are selectively energized by selectively closing said first switch means, an alarm, second switch means for energizing said alarm, means connecting said second switch means to the junctions between each of said devices and said first switch means, said second switch means energizing said alarm in response to a decrease in current through any of the junctions between said devices and said first switch means to below the predetermined current through said first switch means when such first switch means is closed.

Claim 14

In combination with a plurality of electrical devices, a circuit for detecting the failure of any of said devices comprising a power source, a plurality of first switch means, a predetermined current flowing through each of said first switch means when closed, means connecting each of said devices and a different one of said first switch means in series, means connecting all of said series connected devices and first switch means in parallel to said power source whereby said devices are selectively energized by selectively closing said first switch means, an alarm, second switch means for energizing said alarm, means connecting said second switch means to the junctions between each of said devices and said first switch means, said second switch means energizing said alarm in response to a decrease in current through any of the junctions between said devices and said first switch means to below the predetermined current through said first switch means when such first switch means is closed.

Claim 15

The combination of claim 8, wherein said second switch means includes a plurality of electronic switches having input, output and control electrodes, means connecting said input and outpUt electrodes to said power source, means connecting a different one of said control electrodes to each of the junctions between said devices and said first switch means, each of said electronic switch means changing state in response to a decrease in the current through the connected junction to below said predetermined current, a common terminal, and means connecting said output electrodes to said common terminal whereby the current through said common terminal is changed upon a failure of one or more of said devices, and means responsive to the current through said terminal for energizing said alarm.

Claim 16

A circuit for detecting the electrical failure of a device which requires a predetermined current to energize comprising, in combination, means for causing a current lower than the predetermined current to flow through the device, the current through the device decreasing to below such lower current in the event of a failure of the device, an alarm, switch means for energizing said alarm in response to such a decrease in the current through the device, a resistor, means connecting said resistor in series with the device, the current to the device being caused to flow through said resistor when the device is not energized, and switch means for selectively shorting said resistor to increase the current in the device to the predetermined energizing current for selectively energizing said device.

Claim 17

A circuit for detecting the electrical failure of a device which requires a predetermined current to energize comprising, in combination, means for causing a current lower than the predetermined current to flow through the device, the current through the device decreasing to below such lower current in the event of a failure of the device, an alarm, switch means for energizing said alarm in response to such a decrease in the current through the device, a resistor, means connecting said resistor in series with the device, the current to the device being caused to flow through said resistor when the device is not energized, and switch means for selectively shorting said resistor to increase the current in the device to the predetermined energizing current for selectively energizing said device.

Claim 18

In combination with a plurality of incandescent lamps, a circuit for detecting the failure of any of said lamps comprising a power source, a plurality of first switch means, each of said first switch means having a predetermined voltage drop when closed, means connecting each of said lamps and a different one of said first switch means in series, means connecting all of said series connected lamps and first switch means in parallel to said power source whereby said lamps are selectively energized by selectively closing said first switch means, an alarm including all of said lamps, second switch means for energizing said alarm, and means connecting said second switch means to the junctions between each of said lamps and said first switch means, said second switch means energizing said alarm in response to a decrease in voltage on any of said junctions between said lamps and said first switch means to below the predetermined voltage drop of said first switch means whereby, when one or more of said lamps fail, the remaining good ones of said lamps are all energized.

Claim 19

In combination with a plurality of incandescent lamps, a circuit for detecting the failure of any of said lamps comprising a power source, a plurality of first switch means, each of said first switch means having a predetermined voltage drop when closed, means connecting each of said lamps and a different one of said first switch means in series, means connecting all of said series connected lamps and first switch means in parallel to said power source whereby said lamps are selectively energized by selectively closing said first switch means, an alarm including all of said lamps, second switch means for energizing said alarm, and means connecting said second switch means to the junctions between each of said lamps and said first switch means, said second switch means energizing said alarm in response to a decrease in voltage on any of said junctions between said lamps and said first switch means to below the predetermined voltage drop of said first switch means whereby, when one or more of said lamps fail, the remaining good ones of said lamps are all energized.