Event Monitor System

Abstract

An event monitoring system for displaying information of the condition of a plurality of condition responsive means which may be electronic switches or relay contacts which have circuit opening and circuit closing conditions indicating two possible conditions (i.e., normal and abnormal) of the condition or variable being monitored. The event monitoring system includes saturable core devices having respective separate saturable cores most desirably each carrying a biasing winding and a scanning winding, the biasing windings being connected in series and the scanning windings being connected in series. The biasing windings have different numbers of turns with respect to one another so a predetermined magnitude of biasing current passing through the series connected biasing windings will saturate the cores to provide progressively increasing degrees of saturation in the cores. The series connected scanning windings have the same or similar numbers of winding turns as each other scanning winding and a scanning current of progressively increasing value is delivered to the scanning windings to develop an oppositely directed progressively increasing electromagnetic field sequentially to unsaturate the cores at predetermined current values to cause sequential electrical output signals to be generated thereby. Associated condition responsive means are connected to each saturable core device, such as across each scanning windings, and the condition responsive means is a normally open switch so closure of the switch will prevent the unsaturation of the core by the scanning current. The absence of an electrical output signal at the current value assigned to the core device involved indicates that the variable involved is normal or abnormal whichever the case may be.

Description

This invention relates to an event monitoring system for displaying the normal and abnormal conditions of a large number of variables or conditions being monitored by activation of condition sensor means associated therewith.

The event monitoring system of this invention has its most useful application in systems wherein the connections between a central control panel and a large number of condition sensors is made over only a few wires, and has its most important (but not its only) utility for sensing and displaying the circuit opening and circuit closing conditions of switching means, such as relay contacts and electronic switches representing normal and abnormal conditions of the devices or condition means being monitored.

One such event monitoring system of the prior art is based on a single-series loop of switches, as in the case of burglar alarms, all of which are closed to indicate that all doors and/or windows of a particular building located remote from a readout panel are secured shut. In this system, a door or window which becomes open will cause one of the switches to be actuated to an open condition this energizing a warning or alarm device at the central location to indicate that a door or window has been opened. However, this type of prior art system is not capable of indicating which particular door or window is opened. Another type of prior art event monitoring system provides a separate indication of the condition of each of a plurality of variables being monitored but these systems, which operate with single circuit opening or circuit closing condition responsive means, require at least one line for each condition responsive switch within the system.

Accordingly, an object of this invention is to provide an electrical event monitoring system for sensing normal and abnormal states of a plurality of condition responsive means which can comprise simple circuit opening or circuit closing switches indicating the normal and abnormal states of the variables or conditions being monitored and wherein a minimum number of lines are required for connecting a monitoring station to the condition responsive means to display the information of the conditions of all the variables or conditions being monitored.

In accordance with the most advantageous form of the invention, there is associated with each condition responsive means a saturable core device including a saturable core having biasing and scanning windings wound on a common saturable core preferably having a rectangular hysteresis characteristic, the biasing winding of each core having a different number of turns with respect to the biasing windings of every other core. The biasing windings are connected in series to receive a biasing current which may be a constant current from a contact amplitude direct current voltage source or a varying direct current from a varying amplitude direct current voltage source to provide the desired biasing magnetomotive force which saturates the associated cores in different degrees depending upon the number of turns in the biasing windings. The scanning windings of the saturable core devices are connected in series one with the other to receive a common progressively increasing scanning current to develop a second magnetomotive force in each saturable core device opposite in direction to the magnetomotive force produced by the biasing current so that the two magnetomotive forces subtract from one another. Therefore, the progressively increasing scanning current may be sufficient to cause the saturated condition of the cores of the saturable core devices sequentially each to go from their initially saturated state through an unsaturated state to their opposite state of saturation, and an electrical output, such as a voltage pulse, is generated during the momentary interval each core is in an unsaturated state. Thus, where, for example, when there are 200 similar saturable core devices numbered 1 to 200 having biasing windings with progressively differing numbers of turns, (e.g., 1 to 200 turns), a progressively increasing scanning current will produce 200 electrical output signals in the windings of the saturable core devices, the output signals occurring at 200 equally spaced intervals over an arbitrary time base. A sensing circuit connected in series with the serially connected scanning or biasing windings thus can sense the presence or absence of electrical outputs generated by all of the saturable core devices.

In one form of the invention the scanning windings are shunted by condition responsive switches which are respectively in circuit opening or circuit closing conditions when the associated devices or condition means are in normal or abnormal conditions or vice versa. Therefore, the closure of a condition responsive switch prevents the scanning current from unsaturating the associated saturable core device so that the absence of a pulse at a time interval assigned to a particular saturable core device indicates that the device or condition means being monitored is either in a normal or abnormal condition, whichever the case may be.

The electrical output sensing circuit, the scanning and biasing current sources, and a condition display means are most desirably located at a central control sation. The scanning current source may be a cyclic sawtooth current generator. The display means may be a gate controlled annunciator system with the condition of each event being monitored indicated by a different visible indication, provided for example, by one or two light sources. A gate circuit may be provided for controllably actuating a selected annunciator control circuit in response to the simultaneous presence of a timing and a gate signal occurring during the time interval of an electrical output assigned to an associated saturable core device, the presence of both signals being required. Another form of display means which can be utilized with this invention is a strip chart recorder of the type providing a permanent mark on a moving paper strip whenever an electrical output is generated by a saturable core device, so that the presence or absence of a mark at a particular point on the strip chart quickly can identify the condition of a particular condition responsive means during the scanning cycle involved. The strip chart recorder may thus display marks at numbered locations on the chart corresponding to a particular condition responsive means being monitored.

The aforementioned gate circuits may include a decoding group of saturable core devices of substantially a similar design and arrangement or the group of saturable core devices located at the remote monitoring points. In this arrangement the biasing and scanning currents are delivered to the biasing and scanning windings of both groups of saturable core devices. The group of saturable core devices located at the central control station will produce electrical outputs in the associated windings which are coupled to the input of separate respection AND gate circuits, the latter electrical outputs being developed at points in time corresponding to the electrical outputs produced by the remotely located saturable core devices when not shunted by their condition responsive switch. The electrical outputs from the remote saturable core devices associated with the condition responsive means being monitored are delivered to the gate circuits through a common signal path and coincident electrical outputs at the input of any gate circuit will actuate the annunciator control circuit associated therewith to operate the associated annunciator lamp.

In one embodiment of this invention the number of saturable core devices which can be used, hence, the number of conditions which can be monitored, for a given amplitude of biasing and scanning current and winding turns variation is doubled by dividing the series connected scanning windings into two groups, the windings in one group being wound in an opposite direction with respect to windings in the other group. Therefore, when all the saturable core devices are saturated in one direction by a given biasing current, a progressively increasing scanning current of a given polarity will generate magnetomotive forces which will be opposing the magnetomotive forces produced by the biasing current in one group of windings while causing aiding of the magnetomotive forces produced by the biasing current in the other group of windings, thus producing electrical output signals only from the one group of windings. When a progressively increasing scanning current, or a biasing current, of opposite polarity is applied to the two groups of serially connected scanning, or biasing windings, the magnetomotive forces generated in said one group of windings will be aiding and the magnetomotive forces in said other group of windings will be opposing, thus producing electrical output signal only from the said other group of windings. In this arrangement there will be two saturable core devices having the same number of biasing winding turns but are distinguishable one from the other by the polarity of the scanning or biasing current applied thereto, the advantage being doubling of the number of saturable core devices which can be used to produce electrical output signals to identify the particular condition responsive means associated with the particular condition event being monitored.

Other objects, features and advantages of this invention will become more fully realized and understood from the following detailed description when taken in conjunction with the accompanying drawings wherein like reference numerals throughout the various views of the drawings are intended to designate similar elements or components.

FIG. 1 is a simplified block diagram of an event monitoring system in accordance with this invention;

FIG. 2 is a partial schematic and partial block diagram of portions of the event monitoring system of FIG. 1;

FIG. 2A illustrates a typical hysteresis curve which may be the magnetic characteristic incorporated in the saturable core devices of this invention;

FIG. 3 is a diagrammatic representation of one kind of display readout which can be used to provide a permanent record of normal and abnormal conditions being monitored by the system of this invention;

FIG. 4 is a simplified block diagram of another form of display readout that can be used in the event monitoring system of this invention;

FIG. 5 illustrates one preferred waveform of scanning current which can be used in conjunction with this invention;

FIG. 6 is a schematic diagram of another form of condition sensor means which may be utilized in accordance with this invention;

FIG. 7 illustrates another preferred form of scanning current which can be used in conjunction with this invention;

FIG. 8 is a block diagram illustrating one circuit arrangement which can be used to form the waveshape of FIG. 7;

FIG. 9 is a schematic diagram of saturable core devices used as the condition sensor means of this invention connected to similarly fashioned saturable core devices used as the decoding means for operation of a plurality of gate control circuits in accordance with one aspect of this invention.

Seen in FIG. 1 is a simplified block diagram illustrating the basic components of an event monitoring system constructed in accordance with this invention. The event monitoring system is indicated generally by reference numeral 10 and includes a central control station 12 wherein the control display equipment 27 and 29 is located which equipment energizes and responds to numerous condition responsive means 22 which may be spaced many miles from the central control station and connected thereto by wires 24, 26, 28 and 30 in a cable 18. Each condition responsive means 22 may include a switch like a thermostat switch which has different states for indicating the normal or abnormal condition of a device or variable 20 being monitored, and saturable magnet core sensor units 16 are provided for developing electrical output signals corresponding to the state of the condition responsive means and occurring at a point in time which identifies particular ones the devices or variables being monitored. The unique and novel aspects of this invention enable a relatively large number of condition responsive means 22 (like 100 or more) switches to be monitored with only a total of four or less interconnecting wires connecting all of these condition responsive means 22 to the central control station 12. Where the condition responsive means 22 are switches, the opening and closing thereof in response to the condition by the monitored device or variable 20 act upon the associated sensor 16 to prevent or inhibit the generation of a signal thereat. These switches may be relay contacts or electronic switches, or any other circuit opening and circuit closing device.

By way of example, the normal and abnormal conditions of the device or variable being monitored 20 being monitored may be represented by the open and closed conditions of the associated condition responsive switch 22 (or vice versa). In this arrangement the associated saturable magnetic core sensor 16 will produce an electrical signal within a reference interval or cycle at a given time assigned to the condition or variable being monitored to indicate the normal condition of the variable. (While in accordance with the broad aspect of the invention, the electrical signal referred to may be the absence of an output but for the purpose of the present exemplary description it will be assumed that the electrical signal referred to is the presence of a voltage or current of a given current or voltage pulse.) When the associated variable is abnormal, the generation of such electrical signal is inhibited. (If the condition responsive switch is to be open when the variable being monitored is abnormal then the presence of such a signal would indicate that the variable involved is abnormal.) The presence or absence of an electrical signal will operate a suitable time and signal responsive readout or annunciator means 29 connected in common with all of the saturable core sensors 16 to indicate which variables are normal and which are abnormal. Various saturable core operating currents are fed to one or more windings of the saturable core sensors on one or more lines like 24 and/or 28 by core operating means 27 and the electrical output signals referred to can be coupled to the readout or annunciator means 29 by the same or different lines. Since lines 26 and 28 may be associated respectively with the lines 24 and 28 or a common ground line may replace the lines 26 and 28 when a suitable earth-ground is readily obtainable between the remote stations in the field and central control stations.

For a better understanding of one of the unique and novel aspects of this invention reference is now made to FIG. 2 wherein the saturable core sensors 16 are indicated schematically. Each of the saturable core sensors is here indicated by reference numerals 32-44 and include separate cores 32a- 44a respectively and associated biasing windings 32b- 44b and groups of scanning windings 32c- 44c. The saturable core sensors or devices 32-44 may be of the toroid type but it is within the contemplation of this invention that saturable core devices of any suitable configuration can be used. The biasing windings 32b-44b are connected in series one with the other so that a common biasing current from a bias current source 48 at the central control station 12 will pass through the biasing windings initially to saturate all of the magnetic cores 32a-44a. In accordance with this invention, the various biasing windings 32b-44b have a different number of turns so as to establish in each magnetic core 32a-44a a different degree of saturation. By way of example, the bias winding 32b may have one turn, bias winding 34b may have two turns, bias windings 36b may have three windings, and so on to the last device which may contain as many windings as there are saturable core devices. The last bias winding 44b of the last saturable core device 44 is connected to the central control station 12 via a common line 30. The scanning windings 32c-44c are also connected in series one with the other for receiving a progressively increasing scanning current from a scan current generator 50 located at the central control station 12, the scanning current preferably increasing linearly with respect to time. The number of turns in each of the illustrated scanning windings 32c-44c is the same. The magnetomotive force generated by the scanning current opposes the magnetomotive force generated by the biasing current to produce a resultant magnetomotive force equal to the difference of the same and over the range of values thereof will sequentially first unsaturate and then drive each core to the opposite state of saturation (i.e., the cores are sequentially rapidly driven from one state of saturation to the other). This action is obtained by using saturable core devices which have rectangular hysteresis characteristics as illustrated in FIG. 2A, this only being illustrated by way of example and not by way of limitation. The endmost scanning winding 44c is connected to an electrical output circuit 46 which, by way of example, comprise a resistor 46a and a capacitor 46b. An electrical output signal is generated as each core is unsaturated and the scanning current as well as the output signals are developed across the resistor 46a but only the output signals are coupled through the capacitor 46b and line 28 to display readout device 52 located at the central control station 12. Each of the condition responsive switches 22 is shown connected in parallel with one of the scanning windings, and if the condition responsive switches are normally open the above described output signals will be generated but the closing of a switch will short circuit the associated scanning winding to prevent the associated core device from being unsaturated by the scanning current. In such case, the absence of a signal during the time interval assigned to the core device indicating that the variable involved is abnormal. On the other hand, if the condition responsive switches are normally closed only a core device which is associated with an abnormal variable will produce a signal during the assigned time interval. The display readout device 52 is designed to give a visual indication of the variables which are normal and/or abnormal during each scanning cycle. Most advantageously the scan current generator 50 and display readout device 52 are operatively interrelated such as by means of a synchronizing circuit 54 to provide a means for identifying the time intervals during which the presence or absence of signals occur to provide the indications of these signals and the identification of the variables represented by these signals or the absence of the same. Also, if desired, the display readout device 52 may be synchronized from signals developed by the scan current generator 50 as delivered over a line 56.

FIG. 3 shows one form of display readout device which may be incorporated at the central control station 12. Here, the display readout device includes a moving tape 58 which passes in proximity to marking heads 60a and 60b which may be respectively actuated by the electric output signals from the line 28 and 56 in FIG. 2. Preferably, the marking head 60a generates cycle beginning markers 59 in the tape 58 from pulses in line 56 generated at the beginning of each scanning current cycle. The marking head 60b generates variable condition indicating markers 61 for each pulse present on the line 28, the presence of which depends on the open or closed condition of condition responsive switch 22 as first explained. The tape 58 may have indicia lines 63 thereon which are marked with numbers as indicated identifying the variable assigned to the various time intervals within each scanning cycle or period represented by the portion of the tape between successive cycle beginning markers 59. Where the abnormal condition of a variable results in the closure of the associated condition responsive switch, the absence of a marker 61 such as at points or interval identified by indicia line numbers 4 and 198 in FIG. 3 indicates that the variable involved is abnormal.

Referring now to FIG. 4 there is seen a readout circuit here designated generally by reference numeral 52b. The display readout circuit 52b includes a gate control scanner 70 for generating signals corresponding in time to the spaced apart signals produced by the condition responsive means 16 of FIGS. 1 and 2, the gate control scanner being any suitable circuit, as for example, a ring counter or the like. Sequential output signals from the gate control scanner 70 are delivered to respective ones of a plurality of AND-gates 71, 72, 73 and 74. Additionally, the spaced-apart electrical output signals on line 28 are simultaneously delivered to all of the AND-gates 71-74 and only that AND-gate having simultaneous input signals will be activated to an open or signal passing condition thus applying an operating signal to an associated bistable control circuits 76, 77, 78 or 79. By way of example, the control circuits 76-79 may be latch relay control circuits for energization relay coils 80, 81, 82 and 83 respectively in response to the output of the AND-gates 71-74. Although relays are shown in the embodiment herein, it will be understood that any suitable bistable or lock-in switching circuit means may be used, as for example, bistable transistor or silicon controlled rectifier circuits. Associated with each of the relay coils 80-83 are corresponding single-pole, double-throw switches having movable contacts 80a-83a connected to a voltage source, as for example a positive voltage supply, and a pair of stationary contacts 80b-80c . . . . 83b-83c thereof connected respectively to visual indicating lamps 86 and 87. Each of the indicating lamps 86 may be a red lamp while each of the indicating lamps 87 may be a green lamp. It will be assumed that the normal conditions of condition responsive switch 22 is to cause energization of the associated green lamp. If the associated relays are normally deenergized, the presence of an abnormal condition will produce a pulse on line 28, and such a pulse together with a corresponding pulse from the gate control scanner 70 will energize, and lock-in the appropriate relay coil to move the appropriate one of the movable contactors 80a, 81a, 82a, or 83a from the contacts 80c, 81c, 82c or 83c to the contacts 80b, 81b, 82b or 83b to deenergize the corresponding green lamp and energizing the accompanying red lamp to readily identify the location of the abnormal condition. Each of the control circuits 76-79 may include suitable switch means 76a-79a or the like selectively to change the function of the control circuit to either energize or deenergize the relay coils 80-83 during the presence or absence or an output of the associated AND-gates 71, 72, 73 or 74, thus selectively changing which conditions are to be indicated as normal or abnormal.

FIG. 5 illustrates an exemplary current waveform 90 developed by the scan current generator 50 of FIG. 2 which is to be used for the scanning current signals applied to the scanning windings 32c-44c as illustrated, the waveform 90 has linearly increasing sawtooth waveform portions 90a each followed by a quick return portions 90c, portions 90a of the waveform each have points indicated by the vertical broken lines 90b occurring at times t.sub.1, t.sub.2, t.sub.3, etc. Within each cycle which are the instants of time when the current waveform will cause unsaturation of the various saturable core devices 32-44. The quick return portion 90c may be used to develop the synchronizing or cycle beginning pulses (as by passing the waveform through a differentiating network) and such pulses fed to the cycle beginning marker generating head 60a in FIG. 3.

Referring now to FIG. 6 there is seen a modified form of the saturable core circuit of this invention and here designated generally by reference numeral 16a. In this form the saturable core devices are divided into two groups, one group including saturable core devices 96, 97, 98, etc., and the other group containing saturable core devices 96', 97', 98', etc. Their biasing and scanning windings 96a-a', 97a-a', 98a-a', etc., and 96b-b', 97b-b', 98b-b', etc., are respectively connected in series to receive the same biasing and scanning currents. In this arrangement, the biasing or scanning windings of one group of saturable core devices are wound in the opposite direction from that of the corresponding windings in the other group of saturable core devices (windings may be said to be wound in opposite directions if their terminal connections are in reverse relation even though actually wound in the same direction from a visual inspection of the same). In the embodiment illustrated therein it is the biasing windings of the two groups of saturable core devices which are wound in opposite directions. In such case the direction of the electromagnetic fields developed by the biasing windings of one group of saturable core devices is opposite that developed by the biasing windings in the other group of saturable core devices. This is indicated by the upwardly directed arrowed lines adjacent the biasing windings 96a-98a, and the downwardly directed arrowed lines adjacent the biasing windings 96a'-98a', etc. A scanning current, similar to that shown in FIG. 5 will operate to unsaturate sequentially the saturable cores of one group of the devices since the waveform 90 will provide a bucking electromagnetic field in one group and an aiding electromagnetic field in the other group of saturable core devices. A modified scanning current waveform is applied to the scanning windings 96b-b', 97b-b', and 98b-b', etc., illustrated in FIG. 7 which is a periodic waveform 105 having linearly increasing positive sawtooth current waveform portions 105a between a periodic waveform having linearly negative current waveform portions 105b. The positive scanning current waveform portions 105a operate in the same manner as the scanning waveform 90 of FIG. 5 to sequentially unsaturable one of the groups of saturable core devices 96-98 and the negative scanning current waveform portions 105b operate in the same manner as the scanning waveform 90 of FIG. 5 sequentially to unsaturate one of the other groups of saturable on devices 96'-98'.

FIG. 8 illustrates an exemplary circuit arrangement which provides means for generating the current waveform 105 of FIG. 7. Here there is provided a clock pulse generator 112 which may comprise any suitable means for producing equally spaced apart pulses, as for example, a free running oscillator of either the sine wave or square wave type the output of which may be connected to a differentiating circuit for producing the desired pulses. The clock pulses are then delivered simultaneously to a sawtooth generator 112 and a bistable flip-flop circuit 113 via lines 112a and 112b respectively. The sawtooth generator 112 may be of any suitable design to produce at the output thereof the desired sawtooth waveform as illustrated by reference numeral 106, as where, for example, the linearly increasing portion of the sawtooth waveform 106 is developed by the initial substantially linear portion of an exponential charging voltage across a capacitor within the sawtooth generator 112. Also, the bistable flip-flop circuit 113 may be of any suitable design to provide at the two output lines 113a and 114b thereof alternately appearing gate opening and gate closing control voltages, the line 113a having a gate opening voltage and the line 113b having a gate closing voltage during one time interval and this condition reversing during a subsequent time interval, and these gate opening and gate closing voltages being developed by, for example, either a saturated or an unsaturated flip-flop circuit having a pair of alternately conductive transistors or the like wherein the outputs of each are cross-coupled to the input of the other in the usual manner. The transistors may be arranged to receive a single common input trigger voltage, as shown here by line 112b, when the emitter electrode of such transistors are connected together and the trigger voltage is applied to the emitters, or the input may be divided to provide connection to the inputs of the two transistors, either of the above input circuit arrangements is well known in the art. The outputs of the bistable flip-flop circuit 113, via line 113a and 113b, are connected to gate control circuits 114 and 115 which also receive the sawtooth waveform 106 and each gate circuit 114 and 115 passing ever other sawtooth waveform depending on which of the lines 113a or 113b is in the gate opening condition. However, at the output of gate circuit 114 there is provided an inverter circuit which reverses the polarity of the sawtooth waveform from gate 114. The two outputs of the gate circuits 114 and 115, one being reversed in polarity, are then recombined at an output line 117 whereat the composite waveform 105 is developed.

Referring now to FIG. 9 there is seen still another form of this invention wherein a group of saturable core devices 140, 141, 142, 143, etc. are provided for location at points at a remote station. The saturable core devices 140-143, etc. have their biasing windings 140b-143b, etc. connected in series and their scanning windings 140c-143c, etc. connected in series in substantially the same manner as described hereinabove. However, in this embodiment there is provided a plurality of decoding saturable core devices 146, 147, 148, 149, etc. of substantially the same configuration as the saturable core devices 140-143, etc. and in a similar manner have their biasing windings 146b-149b, etc. connected in series one with the other and their scanning windings 146c-149c, etc. connected in series one with the other. The biasing winding 146b-149b are connected in series with the biasing winding 140b-143b via a line 24a and the scanning windings 146c-149c are connected in series with the scanning windings 140c-143c via a line 26a. In accordance with this aspect of the invention the saturable core device 140 is substantially the same as the saturable core device 146 while the saturable core device 141 is substantially the same as the saturable core device 147 and so on thus forming two similar groups of saturable core devices. The scanning windings 146c-149c etc. of the decoding cores are free of condition responsive means connected in parallel therewith for shunting the current therethrough. Therefore, during each common scanning current signal through the two groups of scanning windings an electrical output will be developed at each saturable core device of the decoding group and an electrical output will be developed at the remote monitoring group only by those saturable core devices not shunted by their associated condition responsive switch means 22, and the electrical outputs developed by correspondingly similar ones of saturable core devices of the two groups occurring at substantially the same time. The electrical output signals from the scanning windings 140c-143c, etc. are delivered to a pulse detector and amplifier circuit 150 via a line 28a which, in turn, is connected to the line 26a. The electrical output signals developed on the scanning windings 146c-149c are maintained sufficiently low in amplitude as not to affect the pulse detector and amplifier 150 to prevent erroneous condition responses at the display readout. This can be accomplished by providing loose coupling of the winding 146c-149c, etc. or by utilizing saturable magnetic cores 146a-149a, etc. of different materials or configurations with respect to the saturable magnetic cores 140a-143a, etc.

The electrical signals formed at the output of the pulse detector and amplifier 150 are delivered to a plurality of gate circuits 152, 154, 156, 158, etc. The electrical output of the decoding saturable magnetic core devices 146-149, etc. are also delivered to the gate circuits 152, 154, 156, 158, etc. by means of separate signal developing windings 146d-149d, etc. respectively. The output signal from each of the windings 146d-149d, etc., will be coincident only with the output signal of the corresponding one of the windings 140c-143c, etc. and only under this condition will the appropriate gate circuit be electrically opened to pass a signal to a corresponding one of storage circuits 162, 164, 166, 168, etc. Here, the storage circuits 162, 164, 166, 168, etc. may correspond in electrical function to the relay control circuits 76-79, etc. of FIG. 4. Connected to the outputs of the storage circuits 162, 164, 166, 168, etc. are suitable display device 172, 174, 176, 178, etc. respectively, which, if desired may correspond to the pairs of indicating lamps 86 and 87, of FIG. 4. Accordingly, the embodiments disclosed in FIG. 9 illustrates effective and convenient means for accurately developing decoding electrical signals to be applied to the AND-gates 152, 154, 156, 158, etc., the decoding signals corresponding in time to the electrical output signals developed by the saturable core devices located at the remote location. Also, it will be noted that here only three electrical lines are used to interconnect the saturable core devices at the remote location with the central control station since the scanning current line 26a and the electrical output signal line 28a are connected together and may be the same line, the pulse detector and amplifier circuit 150 providing means for separating and/or distinguishing between scanning current signals and electrical output signals.

Accordingly, this invention provides means for monitoring a plurality of conditions between normal and abnormal states thereof by providing suitable readout display of the condition being monitored at a central control station, and the connections between the central control station and a remote location are accomplished over a minimum number of wires. Therefore, it will be understood that variations and modifications of the exemplary embodiments disclosed herein may be effected without departing from the spirit and scope of the novel concepts of this invention.

Claims

I claim:

1. An event monitor system for detecting the presence of an abnormal state of any one of a number of conditions being monitored, said system comprising: a first plurality of saturable core devices each having a winding wound about a separate saturable magnetic core, said windings being connected in series; means for initially saturating said cores in a given direction; means for sequentially driving each magnetic core from a state of saturation in said given direction to an unsaturated state, the driving of each magnetic core from saturation in said given direction to an unsaturated state occurring before the next core is driven from its initially saturated state to provide a detectable substantial change in an electrical output in the said winding thereof as the core thereof is separately driven from its state of saturation; condition responsive means respectively associated with each of said plurality of saturable core devices, each of said condition responsive means being respectively in normal and abnormal conditions when the condition being monitored is respectively in normal and abnormal states and in one condition thereof inhibiting the detectable substantial change in the electrical output of the associated saturable core device so said electrical output in said winding thereof is absent at the instant of time when the core would otherwise be driven from its saturated state; and time and electrical input responsive means coupled to said windings and responsive to the presence or absence of an electrical output in said group of windings at a given time for identifying the associated saturable core device associated with a condition responsive means in an abnormal condition.

2. An event monitor system for detecting the state of a number of conditions being monitored, said system comprising: a first plurality of saturable core devices each having a winding wound about a separate saturable magnetic core, said windings being connected in series; means for initially saturating said respective cores in a given direction in progressively increasing predetermined degrees; scanning current means connected to said series connected winding for generating a progressively increasing current for sequentially driving each core from a saturated condition in said given direction to an unsaturated state, the driving of each magnetic core from saturation in said given direction to an unsaturated state occuring before the next core is driven from its initially saturated state to provide a detectable substantial change in an electrical output in the winding thereof; condition responsive means respectively associated with each of said plurality of saturable core devices, each of said condition responsive means being respectively in normal and abnormal conditions when the condition being monitored is respectively in normal and abnormal states and in one condition thereof inhibiting the detectable substantial change in the electrical output of the associated saturable core device so said electrical output in said winding thereof is absent at the instant of time when the core would otherwise be driven from its saturated state; and time and electrical output responsive means coupled with said windings and responsive to the presence or absence of an electrical output in said group of windings at a given time for identifying the saturable core device associated with a condition responsive means in an abnormal condition.

3. An event monitor system according to claim 2 wherein each of said cores of said saturable core devices are substantially identical and having windings of progressively increasing numbers of turns to develop saturating magnetic fields within their respective cores of correspondingly progressively increasing magnitude and said scanning current means providing a progressively increasing current through said windings.

4. An event monitor system according to claim 3 wherein said means for sequentially driving each magnetic core from a saturation in said given direction will drive said magnetic core through an unsaturated state to the opposite state of saturation, the switchover of each core to the opposite state of saturation occurring before the next core is driven from its initially saturated state.

5. An event monitor system according to claim 4 wherein each of said cores has a rectangular hysteresis characteristic so each core is driven between opposite states of saturation with a small change in ampere-turns.

6. An event monitor system according to claim 2 wherein said condition responsive means is a switch connected across a winding of each magnetic core device to render the core unresponsive to said scanning current when the switch is in its closed condition.

7. An event monitor system according to claim 2 wherein said windings of said first plurality of saturable core devices are divided into two groups, one group of windings being wound in one direction and the other group of windings being wound in the opposite direction, the said time and amplitude dependent scanning current developed by said scanning current means is a series of alternately oppositely directed current signals; one current signal increasing over a predetermined time interval starting at zero and increasing to a maximum of one polarity, and the other oppositely directed current signal increasing over a subsequent predetermined time interval starting at zero and increasing to a maximum of the opposite polarity, said one current signal sequentially driving each core of said one group of windings from a saturated condition in said given direction through an unsaturated state to the opposite state of saturation to produce a detectable substantial change in said electrical output while not effecting a change in said other group of windings, and said other current signal sequentially driving each core of said other group of windings from a saturated condition in said given direction through an unsaturated state to the opposite state of saturation to produce a detectable substantial change in said electrical output while not effecting a change in said one group of windings.

8. An event monitor system according to claim 2 wherein said time and amplitude dependent scanning current developed by said scanning current means is a linearly increasing current over a predetermined time interval which periodically repeats starting from zero and linearly increasing to a maximum value.

9. An event monitor system according to claim 2 wherein the detectable substantial change in the electrical output in each of said windings is produced by a change of state of saturation of the associated saturable core device.

10. An event monitor system for detecting the state of a number of conditions being monitored, said system comprising: a first plurality of saturable core devices each having first and second windings associated with a separate saturable magnetic core, said first windings being connected in series with each other to form a group of biasing windings which, when a given saturating biasing current flows therein, produces progressively increasing degrees of saturation in a given direction in the cores thereof, said second windings being connected in series with each other to form a group of scanning windings; biasing current means connected to said group of biasing windings to cause said given saturating biasing current to flow through each winding of said group of biasing windings to saturate said cores in said first direction in progressing increasing degrees of saturation; scanning current means connected to said scanning windings for feeding a scanning current therethrough which increases progressively in amplitude for sequentially driving each core from a saturation in a given direction through an unsaturated state to the opposite state of saturation, the driving of each magnetic core from saturation in said given direction to an unsaturated state occuring before the next core is driven from its initially saturated state to provide a detectable substantial change in an electrical output in the windings thereof as the core thereof is separately driven from its initial state of saturation; condition responsive means respectively associated with each of said plurality of saturable core devices, each of said condition responsive means being respectively in normal and abnormal conditions when the condition being monitored is respectively in normal and abnormal states and in one condition thereof inhibiting the detectable substantial change in the electrical output of the associated saturable core device so said electrical output is absent at the instant of time when the core would otherwise be driven from its initially saturated state; and time and electrical output responsive means coupled in series with one of said group of windings and responsive to the presence or absence of an electrical output in said group of windings at a given time for identifying the saturable core device associated with a condition responsive means in an abnormal condition.

11. An event monitor system according to claim 10 wherein said biasing means is a direct current voltage source of constant amplitude to provide a steady state of current through each of said biasing windings.

12. An event monitor system according to claim 10 wherein said detector means includes a plurality of annunciator control circuits, a plurality of gate circuits each responsive to an electrical output from a different one of said scanning windings and a second control signal occurring at the same time as developed by a gate control circuit for energizing an associated annunciator control circuit between normal and abnormal conditions, an alarm indicating means connected to each annunciator control circuit to be operated thereby to an alarm indicating condition when said associated annunciator control circuit is in said abnormal condition.

13. An event monitor system according to claim 12 wherein said gate control circuit includes a second plurality of saturable core devices each having a first and second winding associated with a separate magnetic core, each of said first windings being connected in series with each other to form a group of biasing windings which, when a given saturating current flows therein produces progressively increasing degrees of saturation in a given direction in the cores thereof, said second windings being connected in series with each other to form a group of scanning windings, said second plurality of saturable core devices being remote from said first plurality of saturable core devices and arranged for receiving simultaneously the biasing current from said bias current means and the scanning current from said scanning current means substantially in the same manner as the windings of said first plurality of saturable core devices to generate time sequential pulses which are applied to said plurality of gate circuits to be coincident with particular electrical outputs from said first plurality of saturable core devices. to open the gate at predetermined points in time.

14. An event monitor system according to claim 12 wherein said alarm indicating means is a visual indicating means.

15. An event monitor system according to claim 10 wherein the detectable substantial change in the electrical output in each of said windings is produced by a change of state of saturation of the associated saturable core device.