US3636485A

US3636485A - Security alarm system

Info

Publication number: US3636485A
Application number: US797918A
Authority: US
Inventors: Paul Weathers
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-02-10
Filing date: 1969-02-10
Publication date: 1972-01-18
Anticipated expiration: 1989-01-18

Abstract

A security alarm system for protecting restricted access areas against entry by unauthorized personnel. A switch operated by the opening of a gate or door in a wall surrounding the protected area causes a diaphragm-type horn to be operated by means of a solid-state control circuit connected between the switch and the horn. Connected in the circuit is a magnetically operated disarming switch which may be turned to a number of positions. This switch is placed on the inside of a window in the wall so that authorized personnel may through the use of a magnet and by visual reference to indicia on the face of the switch position the switch so as to disarm the system and gain access to the area without operating the horn.

Description

United States Patent Weathers [451 Jan. 18, 1972 4] SECURITY ALARM SYSTEM w h 9 Primary Examiner-Remard A. Gilheany [72] Inventor.- Paul eat ers, 0 Station Avenue, Had- Assistant Examiner R N Ema, Jr

den Heights, NJ. 08035 [22] Filed: Feb. 10, 1969 ABSTRACT App]. No.: 797,918

[52] U.S. Cl ..335/205, 335/207, 340/63 [51] Int. Cl. ..H01h 19/00 [58] Field ofSearch ..335/l53, 205-207; 340/63 [56] References Cited UNITED STATES PATENTS I 3,170,052 2/1965 l-lajos .l'. ..'.........335/207 3,403,363 9/1968 Pearse et al ..335/206 X A security alarm system for protecting restricted access areas against entry by unauthorized personnel. A switch operated by the opening of a gate or door in a wall surrounding the protected area causes a diaphragm-type horn to be operated by means of a solid-state control circuit connected between the switch and the horn. Connected in the circuit is a magnetically operated disarming switch which may be turned to a number of positions. This switch is placed on the inside of a window in the wall so that authorized personnel may through the use of a magnet and by visual reference to indicia on the face of the switch position the switch so as to disarm the system and gain 3 access to the area without operating the horn.

5 Claims, 9 Drawing Figures unauthorized personnel.

The present invention relates to improvements useful in security alarm systems of the type which annunciate the entry of unauthorized personnel into a restricted access area. More particularly the present invention is directed to a lowcost solid-state electromechanical security alarm system useful in protecting areas access to which is normally made available only through doors or gates in a wall or other barrier structure surrounding the area. I

The present invention has particular utility in protecting automobiles against unauthorized entry and in one form provides a highly secure alarm system which causes an annunciator such as a horn or light to be periodically operated over a predetermined time period immediately following the opening of a door in the automobile.

. SUMMARY on THE INVENTION ing an otherwise operative alarm system from annunciating the attempted entry of an automobile or other closed area by In a first embodiment the magnetic switch is placed on the inside surface of a glass window in the automobile so that by use of a permanent magnet-type hand-held key, certain magnetic portions of the switch may be oriented so as to disable or disarm the alarm system to permit authorized personnel to enter the automobile without producing an alarm.

In further accordance with the present invention an improved solid-state driving circuit for a diaphragm-type horn is employed which causes the horn to be periodically sounded once the alarm system has been tripped by an intruder. In an embodiment of this feature the diaphragm-type horn is operated through a SCR or Triac with a variable impedance load means connected in shunt Triac gate and hornterminals. In further accordance with the present invention an electronic latching circuit means is provided for causing the alarm to periodicallysound fora selected period of time after the alarm system has been tripped as by the opening of a door in the automobile and the door thereafter promptly reclosed.

DESCRIPTION OF THE DRAWINGS .Other features and advantages offered by the present invention will be apparent fromthe following detailed description taken in connection with the accompanying drawings in which: 1

FIG. 1 is a diagrammatic representation of a closed restricted access area of a type with which the present invention finds utility;

FIG. 2 is an exploded perspective view of a magnetic switch constructed in accordance with the present invention;

FIG. 3 is a perspective view and side plan view of a disc aperture 14 to prevent the entry of personnel into the area II). The door 18 in conjunction with structure affixed to the walls 12 may be provided with a lock of some form such as a conventional key operated tumbler lock. A switch 20 is provided which senses the position of the door 18 so that when the door 18 is in an open position a control circuit 22 actuates an alarm 24. The alarm may be either audible or visual in nature. Dearming means 26 is provided for-permitting authorized personnel to enter the area 10 without activating the alarm 24. The dearming means 26 may be simply a key-operated switch or a switch which is hidden in some location generally not known to persons other than authorized personnel. The dearming means 26 conventionally merely acts upon the control circuit 22 to prevent the alarm 24 to be activated upon opening of the door 18.

The elements shown in FIG. 1 can be seen to correspond generally to an automobile or other passenger vehicle having doors susceptible of being locked. In many conventional alarm systems for automobiles the switch 20 corresponds to the type of switch commonly used in the doors of automobiles for operating courtesylights. Control circuit 22 is generally comprised of a relay or other electrical devices provided for a latching effect so that once the door 18 has been opened the control circuit 22 continues to activate the alarm '24 whether or not the door 18 is closed after the initial opening.

Again considering the general system depicted in FIG. 1 it will become immediately apparent that if the dearming means 26 is simply a manually operated toggle switch or the like, the

security of the system depends heavily upon the successful hiding of the switch so that a burglar or other intruder will have difficulty in locating the same once the alarm 24 has been sounded. On the other hand the dearming means 26 may comprise an electrical switch operated by a cylindrical tumbler lock mounted on the outside of the vehicle. The owner of the car simply then employs a key to dearm the alarm system prior to opening the door and the same or other key for opening the door itself. The principal disadvantage of the latter arrangement is clearly that of the cost and attendant disfigurement of the automobile in mounting the dearming cylindrical lock. It is also clear that an intruder having the skill to pick the automobile door lock will likely possess skillto pick the lock on the dearming means 26.

form of permanent magnet employed in the present invention;

FIG. 4 is a diagrammatic representation of a magnetic read relay;

shown in FIG. 1;

FIGS. 6(a), 6(b) and 6(c) (collectively termed FIG. 6) by perspective side plan and top plan views show one form of key useful in operating the magnetic switch shown in FIG. 1; and

FIG; 7 is a schematic drawing of an electrical alarm control circuit contemplated by the present invention.

Turning now to FIG. 1 there are'shown in diagrammatic form the elements of a typical restricted access security system for a protected area. The protected area 10 is defined by wall members (or other barrier structure) 12 having an aperture or doorway 14 through which personnel may pass in gaining access to the area 10. Adjacent the doorway 14 there may be a window area 16 covered by glass or other transparent material. A door. or gate 18 is provided for sealing the FIG. 5 is a plan view of the top outside cover of the switch In'accordancewith the present invention a simple form of magnetically operated electrical switch is provided for dearming means 26. In one embodiment of the invention the switch may take the form shown in FIGS. 2 and 3 (like elements bearing like reference numerals) wherein as cylindrical elongated magnetic reed relay 30 is affixed by cement or the like to the bottom outside surface of a flat cylindrical receptacle 32. A relatively flat circular 'disclike permanent magnet 34 is adapted for rotation within the receptacle 32 about axial bearing means 36 and 38. The disc magnet 34 comprises two flat

semicircular members

39 and 40 having the same radius and thickness each of which is composed of highly remanent magnetic material and magnetized perpendicularly through its thickness. The two bodies are joined to each other by an adhesive or other means and are so oriented relative to one another that adjacent outer surfaces of each member are of magneti- 7 very distinct straight line discontinuity in the magnetic field pattern produced by the disc. A front cap member 42 is then placed upon the receptacle 32 so that the disc 34 is contained by front, rear, and sidewall members. In accordance with the present invention a rear cap member 44 is provided which again fits over the receptacle 32. The front member 42, the cylindrical receptacle 32, and the rear cap member 44 are preferably made of a material which is optically opaque and has a low relative magnetic permeability, such as fiber, polyvinylchloride or other plastic.

- As can be seen in FIG. 2, the terminals of the magnetic reed relay 30 have connected to them

respective wires

46 and 48 which pass through an aperture 50 in the wall of the rear'cap 44 whereby the relay may be employed as a disarming switch in a remote control circuit as will be described.

.FIG. 4 shows diagrammatically in more detail the essential nature of reed relay. Conventionally, a reed relay such as 30 comprises a closed hollow cylindrical body 52 made of glass or other material havinga low relative magnetic permeability. Within the body 52 are at least two movable coacting electrical contact members such as 54 and 56 which part from and touch one another in response to the magnitude of magnetic flux which passes through the body along a line intersecting the body such as the axis line AA shown in FIG. 4. When magnetic line of force of sufficient density pass along the line AA, for example, in the direction of arrow 58, the

contact members

54 and 56 will be attracted to one another and thereby touch one another to cause the reed relay to assume an electrically closed condition. In the absence of a'magnetic field of sufficient density along the line AA, the

contact members

54 and 56 will be spring biased apart from one another and establish the reed relay in an electrically open condition. A relay of this type is generally referred to as being normally open.

Turning now again to FIG. 2, it will he therefore seen that the reed relay 30 will be in an electrically closed condition whenever the disc 34 is oriented in any position such that the highly directional substantially straight line discontinuity in themagnetic field pattern produced thereby is not in alignment with the axes A-A of the reed relay. Thus, in the orientation shown between the parts in FIG. 2 this straight line discontinuity produced by the disc is shown in substantial alignment with the axis A--A of the reed relay 30 and hence the magnetic switch assembly may be considered to be set in a magnetic null" condition, and in an electrically open condition.

In further accordance with the present invention, and again referring to FIG. 2, and more particularly the cylindrical receptacle 32, there is provided first and

second bodies

62 and 64 of soft iron which may be tin plated. The bodies are made sufficientlywide so that when the disc magnet 34 is oriented such that the straight line discontinuity produced thereby is in substantial alignment with the axis A-A of the reed relay (i.e., in a null position) the disc will not be repelled in either direction so as to close the reed relay. On the other hand the

members

62 and 64 are made sufficiently narrow so that the disc magnet does not tend to lock in the null position.

In further accordance with the present invention, the font cap 42 is provided on its outer surface with an arrangement of visual indicia such as generally shown in FIG. 5. The visual indicia are of a character and are so positioned relative to one another as to aid a human being to visually define predetermined sectors of a circle which in turn is generally defined by the geometric projection of the disc 34 upon the outer wall surface of the front member 42. As shown in FIG. 5, the indicia may correspond to the numbers on the face of a clock as indicated generally at 66. The purpose of these indicia will be immediately perceived by referring to FIGS. 6(a), 6(b), and 6(0) which illustrate a key indicated generally by the numeral 70 in FIG. 6(b). The key 70 comprises a holding member 72 cylindrical in nature and adapted to receive a disc magnet 74 which is comprised preferably of two

magnetic sectors

76 and 78 shown in FIG. 6(a) of generally the same character as the

sectors

39 and 42 which comprise the disc magnet 34 in FIG. 2. The holding means 72 has a protuberance 80 thereon adapted to be grasped by the fingers of the human hand for manipulating the position of the holding member 72. An arrow or other indicia '82 is provided on the rear surface 84 of the holding means 72 and the straight line magnetic discontinuity produced by the magnet 74 is placed in alignment with the arrow 82.

Referring now to FIG. 3 and FIG. 6(b), it can be seen that by placing the key member 70 immediately adjacent the outer surface of the front cap 42 the angular position of the disc magnet 34 can be controlled by merely rotating the key 70. In the preferred form of the invention, the materials forming the

magnetic discs

34 and 74 and the strength of their respective magnetizations is such that there is sufiicient magneticforce introduced between the

disc magnets

34 and 74 to overcome any frictional restraint that may exist within and between the disc 34 and the receptacle bearing 38, when the key is placed adjacent the front cap 42 by a distance up to 120 times the spacing between the reed relay 30 and the disc magnet 34.

As will be seen more clearly hereinafter, the magnetically responsive electrical switch of the present invention as described is an effective dearming means for an alarm system of the general character shown in FIG. 1-. Briefly stated, it is anticipated that the magnetic switch will be positioned on the inner surface of the glass window 16 diagrammatically shown in FIG. 1 so that the key 70 may be used on the outside of the glass to position the disc magnet 34 in any prescribed orientation that may be desired. Thus, if one knows what the relative position is of the reed relay axis A--A relative to the indicia on the face of the front cap 42, one then need only align the arrow 82 of the key 70 with this axial position and the disc magnet will thereafter be caused to orient itself such that the reed relay 30 is in an open condition.

Turning now to FIG. 7 there is shown in schematic form a solid-state security alarm system in accordance with the present invention. The elements of FIG. 7 may be broken down into the same functional groups as depicted in FIG. 1. More particularly, the elements within dotted line area 20' correspond to the door position switch sensing means 20 shown in FIG. 1. The elements within dotted line area 22' generally correspond to the control function means 22 in FIG.

1 The elements shown in dotted line area 24' in turn Within the dotted line area 22' the switch element embraced within the dotted linearea 26 corresponds to the dearming means 26 shown in FIG. 1 and in accordance with the present invention may comprise the magnetically operated switch means earlier described. hereinbefore in connection with FIGS. 2 through 6.

Considering FIG. 7 in more detail,.the door position sensing switch elements within the dotted line area 20 comprise switch means and 92. By way of example, these switches are shown connected in two respectively different configurations commonly found in automotive vehicles for causing courtesy lights within the automobile to turn on when a door is opened. Switch 90 adapted to actuate lamp 94 by connecting one of the lamp terminals to ground is commonly referred to as a normally grounded switch configuration while switch 92 which operates to connect its associated lamp terminal to plus battery is referred to as a normally ungrounded switch con-' figuration. Various manufacturers configure the wiring systems in their automobiles in either one or both of the foregoing types. Switches 90 and 92 are mechanically positioned in the door frames of an automobile such that they are normally open when the doors are closed (as shown in FIG. 7), and cause their respective courtesy lamps 94 and 96 to operate when the corresponding door is opened. Another courtesy lamp 96 is associated with switch 92.

Examining the circuit of FIG. 7 further, it is seen that terminal 90 of switch 90 is connected through resistor 98 to the base of transistor 100. Terminal 92' of switch 92 is connected through a diode 102 to the left-hand terminal of normally opened magnetically operated switch 30'. The other terminal of switch 30' is connected to the upper terminal of a capacitor 104, the lower terminal of which capacitor is connected to circuit ground. The upper terminal of capacitor 104 is in turn connected to the base of a transistor 106 whose collector 108 is connected through a main power on-off switch 110 to a plus battery indicated at 112. The emitter 114 of transistor 106 is connected to the base of transistor 116 with resistor 118 being connected between the emitters of the

transistors

106 and 116. A resistor 120 is then connected to an emitter of transistor 116 to the gate terminal 122 of a Triac or SCR 124. I

the left-hand terminal switch 110 with the other operating load terminal being connected via circuit path 126 to the gate 128 of a power Triac or SCR 130. The load terminal 132 of Triac 130 is then connected to plus power supply of potential terminal 1 12 while its other load terminal 134 is connected to the first operating terminal 136 of a diaphragm-type horn the elements of which are generally shown within the dotted line rectangle 24'. The second operating terminal 138 of the horn 24 is connected to circuit ground.

Continuing further with the description of the circuit shown in FIG. 7, the collector of transistor 100 is shown also connected to one terminal of the magnetically operated switch 30' with resistor 140- connected between that connection point and circuit ground. The parallel combination of resistor 146 and capacitor 148 is connected between the base transistor 106 and the control or gate terminal 128 of Triac 130. A variable impedance circuit is also connected between the control terminal 128 of the Triac 130 and circuit ground. This variable impedance circuit in. accordance with the present invention comprises capacitor 150, resistor 152, re-

sistor 154, and transistor 156 connected as shown in the drawing. The first operating terminal 136 of the horn 24' is connected to the control terminal or gate of Triac 134 through resistor 158.

Completing now the description of the circuit shown in FIG. 7, it can be seen that the emitter of transistor 100 is connected through resistor 160 to the collector of transistor 108 while resistor 162 is connected from the collector 108 to the base of transistor 106.. i

The operation of the circuit arrangement shown in FIG. 7 will now be considered. As previously described, the magneticall'y. operated switch 30 although being based upon a normally open reed relay switch will, when the alarm system is in an armed condition, assume a closed position. This cor responds to the magnetic disc 34 shown in FIG. 2 being turned 'to a position whereat the straight line magnetic discontinuity produced thereby is not in aligned orientation with the axis A-A of the reed relay 30.- When the power switch 110 is therefore closed, and the doors associated with switches 90 and 92 are closed, (the switches 90 and 92 then assuming an open condition) the upper terminal of capacitor 104 will be at substantially ground potential. Upon the opening of the door associated with switch 92, positive power supply potential will be applied through diode 102 to a capacitor 104 thereby charging the same to a point causing the normally nonconductive transistor 106 to become conducting. This in turn causes transistor 116 to become conducting and apply an input signal to SCR 124 causing it to in turn conduct. Conduction of switch 124 in turn supplies a control signal to Triac 130 causing it to become conducting.

Upon conduction of the Triac'130 current will immediately 7 with contact 204, thus causing an interruption in the current both through the coil 200 and the Triac 130. Due to the inductance of the coil 200 a highly negative voltage swing will appear at the operating terminal 136 of the horn shortly following which the armature-202 will return to its contacting position with contact 204 so as to again permit current to be drawn through the Triac 130 to again actuate the winding 200 and draw the armature 202 away from the contact 204. This action is well known and common to present day diaphragmtype horns.

Attention, however, is drawn to the fact that due to the aforesaid swing of terminal 136 to a highly negative potential upon the opening of the contact 204 the average current through the Triac 130 and hence through the horn 24 will be relatively small.

To overcome the adverse effect of the negative swing of terminal 134 the present invention-contemplates imposing an impedance across the operating terminals of the horn. If it is desired that the horn operate substantially continuously while the door remains open a resistance means 206 shown in dotted line may be placed across the operating terminal of the horn in series with the resistance 158 one terminal of which is connected to gate terminal 128.

In a preferred form of the present invention, however, instead of a fixed resistance such as indicated at 206 a-variable resistance threshold network is provided. This network comprises the

elements

150, 152, 154 and 156 previously described. In the operation of this variable resistance network the capacitor 150 begins to charge immediately upon conduction of the Triac 130. The charging current of the capacitor 150 through the base emitter path of transistor 156 causes the transistor to become conductive thereby effectively imposing resistor 154 between the Triac gate terminal 128 and ground while placing resistor 154 and resistor 158 in series combination in shunt with the horn 24. Depending upon the value of the capacitor 150 the horn will continue to operate for a period of time until capacitor 150 has charged to a point where transistor 156 becomes nonconducting. Capacitor 152 will then gradually lose its charge through

resistors

152 and 158 until such time as the transistor 156 again becomes conducting and the horn operated.

Under normal circumstances an intruder upon hearing the horn operate would immediately close the door of the automobile thereby opening switch 92. The present invention therefore provides means for causing the horn to continue periodic operation for a predetermined time period after the door has been closed. This feature is provided for by means of resistor 146 connected between the control terminal of Triac 130 and the upper terminal of capacitor 104. Resistor 146 acts as a direct current feedback means from the Triac 130 so as to recharge the capacitor 104 on a relatively slow basis during operation of the circuit and to at least in part supply adequate current for the operation of the

amplifiers

114 and 116 for some time period, say 4 to 6 minutes after the door associated with switch 92 has beenreopencd.

In the event the automobile door switch is electrically wired as indicated by switch 90, that is the switch is directly connected to ground the opening of the door associated with the switch will cause the switch to close and thereby ground potential to the base of transistor 100. When this occurs, transistor will conduct and cause a positive potential to appear at the left-hand terminal of switch 30'. This positive potential will again cause the circuit to operate in the fashion previously described in connection with the closing of switch 92.

In summary therefore, in protecting a closed area such as an automobile the owner takes the key 70 and manipulates the disc magnet within the magnet switch until the reed relay therein is permitted to assume its normally open condition. The power supply switch in FIG. 7 then closes and the owner locks the vehicle doors. Just before leaving the vehicle unattended, he again employs the key 70 to reposition the disc magnet to some arbitrary position away from that orientation of the same which causes the reed relay 30 to assume its normally open condition. Upon returning to the vehicle, the

operator or owner employs the key 70 to position the magnetic disc to permit reed relay 30 to assume its normally open condition upon which the owner can then enter the automobile without operating the horn. 1

Having thus described my invention what I claim is:

1. In an electrical switch apparatus useful in restricted acemanating therefrom initially extending from said surface in a direction substantially normal thereto, the flux pattern produced by said lines of magnetic force having at least one substantially straight line discontinuity therein along which line a specified magnitude of magnetic flux is defined, said discontinuity being characterized by the lines of magnetic force which emanate from said surface on one side of said discontinuity extending in a direction of magnetic flux flow which is opposite to the direction of magnetic flux flow characteristic of the lines of magnetic force which emanate from said surface on the other side of said discontinuity;

and means mechanically coupled to said support means and said magnetized member for positioning said magnetized member adjacent and in movable spaced relationship to said switch means to permit the selective orientation of said straight line discontinuity in alignment with said specified line intersecting said switch means, the magnitude of magnetic flux defined by said discontinuity along said specified line being of a value which changes the condition of said switch means between said first and second condition when said discontinuity is moved into and out of alignment with-said specified line intersecting said switch means.

2. Apparatus according to claim 1 wherein said magnetized member comprises a relatively flat circular disk having two substantially planar opposing surfaces and wherein said means for positioning said magnetized member comprises a first bearing means positioned at the axis of circular rotation of said disk and a second bearing means carried by said support means cooperating with said first bearing means for permitting rotation of said magnetized member relative to said switch means in close juxtaposition thereto and wherein the flux patterns of the magnetic lines of force emanating from both surfaces of said disk are substantially identical in character such that the substantially. straight lined discontinuity in each flux pattern lies in a common plane.

produced by the magnetic lines of force emanating from either surface of said magnetized member, said magnetic field being of sufficient magnitude to produce a magnetic rotational force upon said magnetized member to produce rotation thereof when said manipulatable means is placed adjacent said magnetized member but spaced apart therefrom by a distance less than times greater than the spacing between said magnetized member and said switch means whereby through manipulation of said manipulatable means the discontinuities in the flux patterns produced by said magnetized member and said manipulatable means coact to permit manually directed changes to be made in the position of said magnetized member relative to said switch means.

5. Apparatus according to claim 2 wherein said support means comprises a receptacle having a front, a rear and a sidewall member and wherein said switch means is fixedly positioned adjacent said rear wall member and said magnetized member is positioned intermediate said switch means and said front wall member and wherein the outer surface of said front wall member bears visual indicia so positioned thereon as to aid a human being in defining predetermined sectors of a circle and wherein at least the front wall member of said receptacle comprises a material having relatively low magnetic permeability and wherein the thickness of the front wall member is no greater than 120 times the distance between said switch means md saig m agnetized member.

Claims

1. In an electrical switch apparatus useful in restricted access security systems comprising the combination of: magnetically responsive switch means comprising at least two movable coacting electrical contact members which part from and touch one another in response to the magnitude of magnetic flux passing through said switch means along a specified line intersecting said switch means to establish said switch means in either a first electrically open condition or a second electrically closed condition; support means carrying said switch means; a permanently magnetized member having at least one substantially planar surface with the lines of magnetic force emanating therefrom initially extending from said surface in a direction substantially normal thereto, the flux pattern produced by said lines of magnetic force having at least one substantially straight line discontinuity therein along which line a specified magnitude of magnetic flux is defined, said discontinuity being characterized by the lines of magnetic force which emanate from said surface on one side of said discontinuity extending in a direction of magnetic flux flow which is opposite to the direction of magnetic flux flow characteristic of the lines of magnetic force which emanate from said surface on the other side of said discontinuity; and means mechanically coupled to said support means and said magnetized member for positioning said magnetized member adjacent and in movable spaced relationship to said switch means to permit the selective orientation of said straight line discontinuity in alignment with said specified line intersecting said switch means, the magnitude of magnetic flux defined by said discontinuity along said specified line being of a value which changes the condition of said switch means between said first and second condition when said discontinuity is moved into and out of alignment with said specified line intersecting said switch means.

2. Apparatus according to claim 1 wherein said magnetized member comprises a relatively flat circular disk having two substantially planar opposing surfaces and wherein said means for positioning said magnetized member comprises a first bearing meaNs positioned at the axis of circular rotation of said disk and a second bearing means carried by said support means cooperating with said first bearing means for permitting rotation of said magnetized member relative to said switch means in close juxtaposition thereto and wherein the flux patterns of the magnetic lines of force emanating from both surfaces of said disk are substantially identical in character such that the substantially straight lined discontinuity in each flux pattern lies in a common plane.

3. Apparatus according to claim 2 wherein there is additionally provided at least one body of low remnance magnetically permeable material held by said support means in close juxtaposition to said switch means at a position along said specified line intersecting said switch means.

4. Apparatus according to claim 2 wherein there is additionally provided a manually manipulatable means for producing a magnetic field having a flux pattern with at least one substantially straight line discontinuity therein of a character substantially identical to the discontinuity in the flux pattern produced by the magnetic lines of force emanating from either surface of said magnetized member, said magnetic field being of sufficient magnitude to produce a magnetic rotational force upon said magnetized member to produce rotation thereof when said manipulatable means is placed adjacent said magnetized member but spaced apart therefrom by a distance less than 120 times greater than the spacing between said magnetized member and said switch means whereby through manipulation of said manipulatable means the discontinuities in the flux patterns produced by said magnetized member and said manipulatable means coact to permit manually directed changes to be made in the position of said magnetized member relative to said switch means.

5. Apparatus according to claim 2 wherein said support means comprises a receptacle having a front, a rear and a sidewall member and wherein said switch means is fixedly positioned adjacent said rear wall member and said magnetized member is positioned intermediate said switch means and said front wall member and wherein the outer surface of said front wall member bears visual indicia so positioned thereon as to aid a human being in defining predetermined sectors of a circle and wherein at least the front wall member of said receptacle comprises a material having relatively low magnetic permeability and wherein the thickness of the front wall member is no greater than 120 times the distance between said switch means and said magnetized member.