before explaining the invention in detail , it is to be understood that the invention is not limited in its application to the detail of construction and arrangement of parts illustrated in the drawings since the invention is capable of other embodiments and of being practiced or carried out in various ways . it is also to be understood that the phraseology or terminology employed is for the purpose of description only and not of limitation . referring to the drawings , fig1 shows a preferred arrangement of a monopolar charge coupled motion detector according to the present invention . the apparatus includes conductive sensor electrode , 2 , connected to analog impedance convertor , 4 , made with mos transistor , bias resistor , 5 , input capacitance , 6 , coupling capacitor , 7 , gain stage , 8 , window comparator , 9 , and power supply , 10 . while rest of the electronic circuit may be shielded , the electrode , 2 , is exposed to the environment . the moving object to be detected is represented by a person , 1 . clothing is usually fabricated from either natural or man - made materials . when the person moves , parts of its dress also move resulting is localized frictions . this causes appearance of electric charges on the surface of dress and skin . usually , air contains either positive or negative ions which can be attracted by the human body . this also changes the body &# 39 ; s electric potential . in fig1 for illustration purposes this is exemplified by positive charges distributed along the person &# 39 ; s body . being a charge carrier , person , 1 , generates electric field , 3 , having intensity , e . the field induces charges of opposite sign in the sensor electrode , 2 . under the static conditions , when the person , 1 , is not moving , the field intensity , e , is constant and the input capacitance , 6 , is discharged through the bias resistor , 5 . that resistor must be selected of a high value : on the order of 10 9 ohms or higher to make the circuit sensitive to relatively slow motion . when person , 1 , moves , intensity , e , of electric field , 3 , changes . this results in appearance of electric voltage across the bias resistor , 5 , and the varying voltage , 23 , at the output of the impedance convertor , 4 . varying voltage , 23 , is fed through the coupling capacitor , 7 , into gain stage , 8 , whose output signal , 28 , is further directed to the window comparator , 9 . the window comparator compares signal 28 , with two thresholds , as it is illustrated in the timing diagram of fig3 a . one threshold , 25 , is normally higher than the signal , 28 , while the other threshold , 26 , is lower than the signal , 28 . when the person moves , signal , 28 , deflects either up or down , causing comparator , 9 , to generate the output signals , 11 . as shown in fig3 b , these signals are square pulses which can be utilized and further processed by conventional data processing devices . the gain stage , 8 , and a window comparator , 9 , are of a conventional design and not described here in details . generally , the thresholds , 25 and 26 , should be separated sufficiently from the static level of signal , 28 , to prevent false triggering from various noise sources . there are several possible sources of interference which may cause spurious detections . among noise sources are 60 ( or 50 ) hz power line signals , electromagnetic fields generated by radio stations , power electric equipment , lightnings , etc . most of these interferences generate electric fields which are distributed around the detector quite uniformly and , can be compensated for by a symmetrical input circuit . fig2 shows a differential input amplifier , 16 , with a high common mode rejection ratio . the input stage must have a very high input impedance . jfet or cmos circuits preferably should be used . both positive , 14 , and negative , 15 , inputs are terminated to ground by networks similar to those of fig1 consisting of resistors , and capacitors : 17 , 18 and 19 , 20 . two inputs of the amplifier , 16 , are connected respectively to two sensor electrodes , 12 and 13 . each sensor electrode is coupled to the environment in its corresponding direction . the sensitivity patterns are represented by the curves , 22 , 24 and arrows , 21 . it follows from those curves , that the maximum sensitivity can be observed along the normal to the electrode surface direction . lowest sensitivity occurs in the direction where both electrodes are equally exposed to the object . the sensor electrode shape is an important factor in the formation of the sensitivity pattern . depending on the actual requirements , the electrodes may be placed differently with respect to each other and to the detector . this is exemplified by fig4 - 7 . in fig4 the electrodes , 12 and 13 , are positioned along the detector &# 39 ; s housing , 27 , which may be shielded to reduce possibility of spurious oscillations . it was found experimentally , that a grounded shield near the electrodes may reduce the range of the detector . a detector should be positioned in such a way as to reduce possible discharge paths between its electrode and moving objects . use of a floating power supply and transmission of output signals via an optical or a radio wave communication channel may significantly improve sensitivity . fig5 shows that sensor electrodes , 31 and 32 , are shaped in the form of conductive tapes . in fig6 sensor electrodes , 33 and 34 , are perpendicular to each other , while in fig7 the electrodes , 35 and 36 , are positioned in the same plane . it practice , it may be desirable to conceal the motion detector and electrodes or camouflage them for the security , aesthetics or other reasons . since electric field can propagate through many materials , the charge coupled detector may virtually &# 34 ; see &# 34 ; through optically opaque objects . therefore , the electrodes and the detector could be hidden inside a wall , in window or door frames . they also could be located inside book covers , file cabinets , desks , etc . the electrodes could be shaped in various forms , like wires , tapes , spheres , panels , etc . they also could take shapes of various things , like paper weights , vases , desk lamps , picture frames , toys , etc . a thin conductive coating on the surface of galss , ceramic or plastic also can function as an electrode . as an example , fig8 shows a vase , 42 , positioned on a base , 45 . a portion of the vase surface is metallized forming an electrode , 43 , which is connected to the detection circuit , 46 , via a conductor , 44 . practically , any conductive media may be used as an electrode . for instance , water in a fish tank can function as an electrode if connected to a charge coupled motion detector of the present invention through an immersed conductor . if a symmetrical circuit is used , like the one shown in fig2 the areas of two electrodes should be identical to assure a good interference reduction . the charge coupled detectors can be used for the security purposes , for energy management , for toy and novelty product manufacturing and other areas where a motion detector should be concealed and where a circular field of view is desirable at relatively short distances up to 10 - 15 ft . since a charge coupled motion detector responds to a charge carried by an object , its detecting ability may be reduced under such environmental conditions when charges are formed with a low rate . for instance , high humidity , conductive floors and wet dress may significantly diminish charge formation . to enhance the reliability of the detector and to increase its range , an active operating mode can be used . in the active mode , an additional device is required to generate electric field in the vicinity of the motion detector . fig9 shows a high voltage source , 37 , which is connected to the conductive element ( strip ), 41 , positioned inside a corridor wall . the source , 37 , generates high constant voltage on the order of 1 , 000 volts . this results in electric field , e , toward the electrodes , 38 and 39 , which are connected to the detector , 27 . all these components are concealed under the wall surface . when an object , 1 , moves into the volume of space filled with electric field , e , its presence will disturb a charge which is induced on the electrodes , 38 and 39 , causing a detection . the disturbed field is shown in fig9 as shorter arrow lines . although the present invention has been described with respect to details of certain embodiment thereof , it is not intended that such details be limitations upon the scope of the invention . it would be obvious to those skilled in the art that various modifications and substitutions may be made without departing from the spirit and scope of the invention as set forth in the following claims .