Condition Detection And Alarm System

Abstract

A condition detection and alarm system is disclosed having a normally inactive detector relay in series in a detection circuit with a normally open-circuited alarm sensing device that is connected in multiple with a resistor to permit supervising of the circuit. In response to actuation of the detector relay, an alarm circuit becomes energized for actuation of at least one alarm device. A single transistor switch is provided for supervising both the detection circuit and the alarm circuit, the detection circuit being supervised in a biasing circuit for the transistor, and the alarm circuit being supervised in the output circuit of the transistor. Failure of the transistor to provide an output is manifested as a trouble condition.

Description

While the invention is subject to a wide range of applications, it is especially suited for use in a condition detection and alarm system wherein both a condition-sensing detection circuit and an alarm circuit are supervised, and the invention will be particularly described in that connection.

It is a requisite in a fire alarm system for use in a public building, such as a school, for example, that fire-sensing detection circuits and alarm circuits be supervised by checking their continuity. Such a system may have a detection circuit for one or more normally open-circuited, condition-sensing devices, and may have an alarm circuit having one or more normally inactive alarm devices, such as bells, connected thereto for use in automatically sounding a general alarm in response to an abnormal condition sensed by the detection circuit. A sensitive supervisory relay is normally included in series in each of these circuits and is maintained energized by a relatively low level of energization of the associated circuit for supervisory purposes, while a detector relay requires a higher level of energization. The use of marginal relays in this manner produces operating problems due to voltage fluctuation.

An object of the present invention is to provide a condition-sensing and alarm system having improved supervisory control.

SUMMARY OF INVENTION

The present invention provides a condition-sensing and alarm system having a normally inactive detector device in a detection circuit and having a normally inactive alarm circuit controlled by the detection device. A single solid-state switching device is controlled partly by the detection circuit and partly by the alarm circuit to deliver an output for manifesting trouble in the continuity of these circuits.

For a better understanding of the present invention, together with other further objects thereof, reference is had to the following description, taken in connection with the single FIGURE of the accompanying drawing.

With reference to the accompanying drawing, terminals (BX) and (CX) are connected to an alternating current commercial source of power, thus these terminals are energized except under commercial power failure conditions. This alternating current energy is applied through a transformer 10, full-wave rectifier 11 and front contact 12 of a power failure relay K1 to direct current power supply terminals (+) and (-) to provide a power supply for the condition-sensing and alarm system. A standby battery 13 can be provided as illustrated to be connected by back contact 12 of relay K1 to the direct current power supply terminals in case of failure of the commercial source of power.

The detection circuit that is supervised comprises wires 14 and 15 and includes a normally inactive detector relay K3 in series in the circuit. The alarm circuit that is supervised includes wires 16 and 17 having a plurality of alarm devices 18 connected thereto.

A single transistor switch 19 is used for supervising both the detection circuit and the alarm circuit. It has its bias determined by the detection circuit and has a supervisory device in the form of relay K4 connected in its output circuit.

Relay K4 is normally energized dependent jointly upon continuity being maintained in both the detection and the alarm circuits to deliver an output of the transistor 19. If either of these circuits becomes open circuited, the relay K4 becomes deenergized to manifest a trouble condition and cause the energization of a trouble lamp 20.

Considering the structure of the supervised circuits more specifically, the detection circuit has a plurality of fire-sensing devices 21 connected in multiple across the wires 14 and 15. These devices 21 are normally open circuited but close their contacts upon sensing an abnormal condition such as a fire. Connected in multiple with the sensing devices 21, is a resistor 22, which normally limits the current flow in the detection circuit. This circuit extends from (+), including wire 14, resistor 22, wire 15, winding of relay K3 and resistor 23, to (-). Because of the resistor 22 being in series in the circuit just described, the circuit is energized at a low level which does not actuate relay K3 to close its front contacts.

The detection circuit just described also serves as a bias circuit for transistor 19 in that a desired level of energization is applied from this circuit to the base of transistor 19 to maintain that transistor normally turned on, dependent upon continuity in the detection circuit just described. OUtput of the transistor 19 to energize the supervisory relay K4 is also dependent upon continuity in the alarm circuit extending from (+), including back contact 24 of relay K2, wire 17, diode 25, wire 16, front contact 26 of relay K1, winding of relay K4 and collector-emitter circuit of transistor 19, to (-).

Relay K4 is therefore maintained normally energized in accordance with continuity in both circuits, because it can be energized in the output circuit of the transistor 19 only provided the alarm circuit continuity is maintained, and the transistor 19 can be turned on only provided there is continuity in the detection circuit. If either of these circuits should become open circuited, the relay K4 would become dropped away, and the dropping away of that relay would close a circuit for energizing the trouble lamp 20 through front contact 27 of relay K1 and back contact 28 of relay K4. A diode 29 is connected across the winding of relay K4 to provide that this relay will not be dropped away due to a momentary line circuit interruption, and also to protect the transistor 19 from an inductive surge generated by the winding of relay K4.

It will be noted that trouble lamp 20 is subject to energization either upon the dropping away of the supervisory relay K4 as described, or upon the dropping away of the power failure relay K1 to close back contact 27. A trouble buzzer 29 is connected in multiple with the trouble lamp 20 through a trouble switch 30 so as to provide an audible manifestation of detection of trouble. The buzzer 29 can be silenced by actuation of the switch 30 to its left-hand position.

If a sensor 21 becomes actuated to close its contacts, the resistor 22 is shunted out of the detection circuit, and thus sufficient current flows in the winding of relay K3 to cause that relay to become picked up. Upon picking up, relay K3 closes a stick circuit including its front contact 31 and cancels button CPB to maintain relay K3 in its picked-up position. The picking up of relay K3 causes the picking up of a repeater relay K2 upon the closure of front contact 32 of relay K3, and the picking up of relay K2 pole changes the alarm circuit so as to render the alarm devices 18 active. Each alarm device 18 (such as a bell or horn) thus becomes energized through front contact 33 of relay K2, wire 16, winding of device 18, a diode 34, wire 17 and front contact 24 of relay K2. The shifting of contacts 33 and 24 of relay K2 thus pole changes the alarm circuit and removes the shunt of the alarm devices 18 by the diode 25.

After the sensors 21 have been restored to their normal conditions, the actuation of cancel push button CPB can become effective to cause relay K3 to be restored to its normally dropped-away position. This causes the dropping away of relay K2 to restore the alarm circuit to its normal polarity of energization.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention.

Claims

What is claimed is:

1. A condition detection and alarm system having at least one normally inactive detection relay serially coupled in a detector circuit including a plurality of normally open sensing devices coupled in parallel with a supervisory resistor, and a plurality of normally inactive alarm-sensing devices coupled in parallel in an alarm circuit subject to activation by the detector devices wherein the improvement comprises:

a. means including a normally conducting transistor for supervising both the detector circuit and the alarm circuit wherein the detector circuit is normally checked for continuity in the base circuit for the transistor and the alarm circuit is checked for continuity in the collector-emitter circuit of the transistor,

b. means including a normally energized relay having its winding connected in the collector-emitter circuit of the transistor deenergized for manifesting failure of continuity in both the detector circuit and the alarm circuit by a cutoff of the conductance of the transistor,

c. a normally energized power failure relay, having a front contact serially coupled in the collector-emitter circuit of the transistor, deenergized upon failure of a commercial source of power to remove the continuity of the transistor circuit; and

d. a standby source of energy coupled to the system upon deenergization of the power failure relay.