Smoke detector failure alarm

Claim 2

An electrical alarm instrument for sensing a physical condition comprising, an electrical alarm, a controlled switch in series with the alarm and having a control, a single, common power supply connected to the alarm and switch, a condition responsive circuit connected to the switch control to close the switch and actuate the alarm in a mode dependent on the power supply, and pulsing means connected between the power supply and the switch control for pulse storage from said common power supply and discharge to the switch control thereby to close the switch and actuate the alarm in a different mode dependent on the pulsing means, the responsive circuit including coupling means connected between the condition responsive circuit and pulsing means responsive to failure in said circuit to render the pulsing means effective, whereby the alarm indicates condition response and circuit failure differently.

Claim 3

An instrument according to claim 1 wherein said pulsing means comprises a resistor and capacitor having a characteristic time constant.

Claim 4

An instrument according to claim 2 wherein said pulsing means comprises a breakdown device connecting said capacitor and switch control when the capacitor is charged to a predetermined voltage effective to open the switch.

Claim 5

An instrument according to claim 1 wherein said power supply cycles at a predetermined rate and said pulsing means stores and discharges at a distinctly different rate.

Claim 6

An instrument according to claim 4 wherein said pulsing means comprises a resistor and capacitor having a characteristic time constant.

Claim 7

An instrument according to claim 4 wherein said power supply comprises a half-wave rectifier.

Claim 8

An instrument according to claim 6 wherein said switch comprises a controlled rectifier tending to open on unrectified half cycles.

Claim 9

An instrument according to claim 7 wherein said alarm comprises an inductance reacting to each unrectified half cycle to maintain power through thE controlled switch during unrectified half cycles.

Claim 10

An instrument according to claim 8 characterized by a unidirectional conducting device connected between the power supply and said capacitor, the switching means of said photo-responsive circuit being effective on circuit failure to connect said device in shunt with the alarm inductance and prevent the inductance from maintaining power through the controlled switch.

Claim 11

An instrument according to claim 1 wherein said responsive circuit includes a photosensitive device and an exciter lamp therefor and said switching means comprises a relay in series with the lamp.

Claim 12

An instrument according to claim 10 wherein said relay actuates a contact connecting the power supply to the pulsing means upon circuit failure.

Claim 13

An instrument according to claim 11 wherein said alarm comprises an inductance reacting to each unrectified half cycle to maintain power through the controlled switch during unrectified half cycles, characterized by a unidirectional conducting device, said relay contact connecting said device in shunt with the alarm inductance upon circuit failure.

Claim 14

An instrument according to claim 10 wherein said photosensitive device comprises a photocell shielded from the exciter lamp and viewing an area illuminated by the lamp, whereby to respond to light scattered by fluid born particles in the illuminated area.

Claim 15

A smoke detector for operation on alternating current comprising, a power supply having positive and negative busses, a smoke sensing circuit, an alarm circuit, and a failure sub-circuit, the power supply including a half-wave rectifier of the alternating current connected to the positive and negative busses, and voltage regulator means connected to the busses, the smoke sensing circuit including an exciter lamp and a relay connected to the busses, and a photocell connected to the busses, the cell being shielded from the exciter lamp and viewing the area illuminated by the lamp; the alarm circuit including an inductive signaling device in series with a controlled rectifier and connected to said busses, the gate of said controlled rectifier being connected to the photocell and responsive thereto to complete a circuit through the signalling device, and the failure sub-circuit comprising a diode, a resistance and a capacitor in series between the busses, the resistance and capacitor having a time constant substantially greater than the current alterations, a gas discharge breakdown device to the junction of the resistance and capacitor and to the controlled rectifier gate, and the relay contact having a position connecting the inductive signalling device to the capacitor and connecting the diode in shunt with the inductive signalling device.

Claim 16

A smoke detector for operation on alternating current comprising, a power supply having positive and negative busses, a smoke sensing circuit, an alarm circuit, and a failure sub-circuit, the power supply including a half-wave rectifier of the alternating current connected to the positive and negative busses, and voltage regulator means connected to the busses, the smoke sensing circuit including an exciter lamp and a relay connected to the busses, and a photocell connected to the busses, the cell being shielded from the exciter lamp and viewing the area illuminated by the lamp; the alarm circuit including an inductive signaling device in series with a controlled rectifier and connected to said busses, the gate of said controlled rectifier being connected to the photocell and responsive thereto to complete a circuit through the signalling device, and the failure sub-circuit comprising a diode, a resistance and a capacitor in series between the busses, the resistance and capacitor having a time constant substantially greater than the current alterations, a gas discharge breakdown device to the junction of the resistance and capacitor and to the controlled rectifier gate, and the relay contact having a position connecting the inductive signalling device to the capacitor and connecting the diode in shunt with the inductive signalling device.