Electromagnetic transducer employing a thin magnetic film having an oriented easy direction of magnetization

Claim 2

An electromagnetic transducer for sensing a movable magnetized storage member and comprising: a. a rigid smooth supporting member. b. a thin magnetizable film having an easy axis of magnetization and being disposed on said supporting member, the plane of the film being substantially normal to that of the magnetized member, said easy axis of magnetization being oriented to be parallel to the direction of magnetization of said magnetized member, c. electrical means parallel to said easy axis for inductivity applying an energizing field to said film thereby to orient the magnetic structure of said film in a desired direction, and d. a sense winding normal to saiD electrical means operably associated with said film effective to detect any changes in the orientation of the internal magnetic structure of the film when said film is brought near an external magnetic field, for providing an output signal indicative of said change.

Claim 3

An electromagnetic transducer for sensing movable magnetized storage members and comprising: a. a rigid smooth substrate, b. a magnetizable thin film having an easy direction of magnetization and overlying said substrate and bonded thereto, said easy direction of magnetization being oriented parallel to the direction of magnetization of said magnetized members, the plane of the film being substantially normal to that of the magnetized members, c. electrically conductive means parallel to said easy axis for applying an electrical field to said thin film thereby to orient the crystalline lattice structure thereof in the hard direction, d. electrical conductive means orthogonally disposed relative to said last-named means for detecting the change in said structure from said hard direction to said easy direction when said film is adjacent an external magnetic field, and e. means adjustably supporting said transducer adjacent a magnetizable record member to enable sensing of the magnetic field in the latter.

Claim 4

An electromagnetic transducer for sensing movable magnetized storage members and comprising: a. a rigid smooth substrate, b. a magnetizable thin film having an easy direction of magnetization and overlying said substrate and bonded thereto, said easy direction of magnetization being oriented parallel to the direction of magnetization of said magnetized members, the plane of the film being substantially normal to that of the magnetized members, c. electrically conductive means parallel to said easy axis for applying an electrical field to said thin film thereby to orient the crystalline lattice structure thereof in the hard direction, d. electrical conductive means orthogonally disposed relative to said last-named means for detecting the change in said structure from said hard direction to said easy direction when said film is adjacent an external magnetic field, and e. means adjustably supporting said transducer adjacent a magnetizable record member to enable sensing of the magnetic field in the latter.

Claim 5

An electromagnetic transducer for sensing a movable magnetized record member and comprising: a. a rigid smooth support, b. a plurality of magnetizable thin films disposed on said support in rows and columns forming a matrix, said films having an easy direction of magnetization oriented parallel to the direction of magnetization of said magnetized members, c. drive conductors for each of said films arranged parallel to said easy direction of magnetization. d. sense conductors for each of said films, e. each of said sense conductors encircling a row of films and disposed at right angles to said drive conductors for operable association with said magnetizable record member having one or more bits of information stored therein as magnetizable spots capable of being sensed by said transducer when said magnetizable member is brought into close proximity thereto.

Claim 6

An electromagnetic transducer for sensing a movable magnetized record member and comprising: a. a rigid smooth support, b. a plurality of magnetizable thin films disposed on said support in rows and columns forming a matrix, said films having an easy direction of magnetization oriented parallel to the direction of magnetization of said magnetized members, c. drive conductors for each of said films arranged parallel to said easy direction of magnetization. d. sense conductors for each of said films, e. each of said sense conductors encircling a row of films and disposed at right angles to said drive conductors for operable association with said magnetizable record member having one or more bits of information stored therein as magnetizable spots capable of being sensed by said transducer when said magnetizable member is brought into close proximity thereto.

Claim 7

An electromagnetic transducer comprising: a. a glass substrate supporting member, b. a thin magnetic film of from 250 to 3,000 angstroms in thickness disposed on a surface of said substrate, c. a first electrical conductor secured to said substrate overlying said thin film and in surface contact therewith, d. a second electrical conductor secured to said substrate at right angles to said first conductor and electrically insulated therefrom, and e. means adjustably positioning said substrate carrying said film adjacent the magnetizable surface of a magnetizable record member for detecting the magnetic field or fields in the latter.

Claim 8

An electromagnetic transducer comprising: a. a glass substrate supporting member, b. a thin magnetic film of from 250 to 3,000 angstroms in thickness disposed on a surface of said substrate, c. a first electrical conductor secured to said substrate overlying said thin film and in surface contact therewith, d. a second electrical conductor secured to said substrate at right angles to said first conductor and electrically insulated therefrom, and e. means adjustably positioning said substrate carrying said film adjacent the magnetizable surface of a magnetizable record member for detecting the magnetic field or fields in the latter.

Claim 9

An electromagnetic transducer comprising: a. a rigid smooth supporting structure, b. a magnetizable film disposed on said supporting structure, c. said film having uniaxial anisotropy resulting in a single easy axis of magnetization in the plane of the film and being capable of assuming either of two stable states of magnetic remanence along said axis, d. energizing means operably associated with said film and parallel to said easy axis for generating a magnetic field transverse to said axis effective to drive said film into the hard or transverse direction, and e. sensing means operably associated with said film and orthogonally disposed relative to said energizing means for operative association with an applied external magnetic field effective to cause said film to switch to one of said stable states, thereby indicating the presence of said external field.

Claim 10

An electromagnetic transducer comprising: a. a rigid smooth supporting structure, b. a magnetizable film disposed on said supporting structure, c. said film having uniaxial anisotropy resulting in a single easy axis of magnetization in the plane of the film and being capable of assuming either of two stable states of magnetic remanence along said axis, d. energizing means operably associated with said film and parallel to said easy axis for generating a magnetic field transverse to said axis effective to drive said film into the hard or transverse direction, and e. sensing means operably associated with said film and orthogonally disposed relative to said energizing means for operative association with an applied external magnetic field effective to cause said film to switch to one of said stable states, thereby indicating the presence of said external field.

Claim 11

An electromagnetic transducer comprising: a. a rigid supporting structure, b. a magnetizable film disposed on said supporting structure, c. said film having uniaxial anisotropy resulting in a single easy axis of magnetization in thE plane of the film and being capable of assuming either of two stable states of magnetic remanence along said axis, d. energizing means operably associated with said film for generating a magnetic field transverse to said axis effective to drive said film into the hard or transverse direction, and e. sensing means operably associated with said film and orthogonally disposed relative to said energizing means for operative association with an applied external magnetic field for causing said film to switch to one of said stable states thereby indicating the presence of said external fields.

Claim 12

An electromagnetic transducer comprising: a. a rigid supporting structure, b. a magnetizable film disposed on said supporting structure, c. said film having uniaxial anisotropy resulting in a single easy axis of magnetization in thE plane of the film and being capable of assuming either of two stable states of magnetic remanence along said axis, d. energizing means operably associated with said film for generating a magnetic field transverse to said axis effective to drive said film into the hard or transverse direction, and e. sensing means operably associated with said film and orthogonally disposed relative to said energizing means for operative association with an applied external magnetic field for causing said film to switch to one of said stable states thereby indicating the presence of said external fields.

Claim 13

An electromagnetic transducer comprising: a. a rigid smooth supporting structure, b. a magnetizable film disposed on said supporting structure, c. said film having uniaxial anisotropy resulting in a single easy axis of magnetization in the plane of the film and being capable of assuming either of two stable states of magnetic remanence along said axis, d. energizing means operably associated with said film for generating a magnetic field transverse to said axis effective to drive said film into the hard or transverse direction, and e. sensing means operably associated with said film and orthogonally disposed relative to said energizing means and to said easy axis of magnetization for operative association with an external magnetic field effective to cause said film to switch to one of said stable states thereby indicating the presence of said external field.

Claim 14

An electromagnetic transducer comprising: a. a rigid smooth supporting structure, b. a magnetizable film disposed on said supporting structure, c. said film having uniaxial anisotropy resulting in a single easy axis of magnetization in the plane of the film and being capable of assuming either of two stable states of magnetic remanence along said axis, d. energizing means operably associated with said film for generating a magnetic field transverse to said axis effective to drive said film into the hard or transverse direction, and e. sensing means operably associated with said film and orthogonally disposed relative to said energizing means and to said easy axis of magnetization for operative association with an external magnetic field effective to cause said film to switch to one of said stable states thereby indicating the presence of said external field.

Claim 15

An electromagnetic transducer comprising: a. a rigid smooth supporting structure, b. a plurality of magnetizable films disposed on said supporting structure, c. said films each having uniaxial anisotropy resulting in a single easy axis of magnetization in the plane of the films and being capable of assuming either of two stable states of magnetic remanence along said axis, d. energizing means operably associated with said films for generating a magnetic field transverse to said axis effective to drive said films into the hard or transverse direction, and e. sensing means operably associated with said films and orthogonally disposed relative to said energizing means for operative association with an applied external magnetic field for causing one or more of said films to switch to one of said stable states thereby indicating the presence of said external field.

Claim 16

An electromagnetic transducer comprising: a. a rigid smooth supporting structure, b. a plurality of magnetizable films disposed on said supporting structure, c. said films each having uniaxial anisotropy resulting in a single easy axis of magnetization in the plane of the films and being capable of assuming either of two stable states of magnetic remanence along said axis, d. energizing means operably associated with said films for generating a magnetic field transverse to said axis effective to drive said films into the hard or transverse direction, and e. sensing means operably associated with said films and orthogonally disposed relative to said energizing means for operative association with an applied external magnetic field for causing one or more of said films to switch to one of said stable states thereby indicating the presence of said external field.

Claim 17

In combination with a movable record member having a magnetizable surface, a transducer comprising: a plane anisotropic thin magnetic film element having an easy axis of remanent flux orientation defining opposite stable states, said film having at least one edge in close proximity to the surface of said record member with the easy axis being angularly displaced from said one edge, and a control winding and a sense winding coupling said film to enable reading of the record member independently of movement thereof.

Claim 18

In combination with a movable record member having a magnetizable surface, a transducer comprising: a plane anisotropic thin magnetic film element having an easy axis of remanent flux orientation defining opposite stable states, said film having at least one edge in close proximity to the surface of said record member with the easy axis being angularly displaced from said one edge, and a control winding and a sense winding coupling said film to enable reading of the record member independently of movement thereof.

Claim 19

The combination of claim 9 wherein said film has a single plane and is positioned with the plane of the film perpendicular to the surface of said record member.

Claim 20

A magnetic sensing unit for reading a movable magnetically encoded storage member having a plurality of magnetically encoded areas, comprising: at least one thin magnetic strip adapted to be positioned contiguous to a magnetically encoded area; the plane of the strip being substantially normal to that of the storage member; drive winding means parallel to the easy axis of orientation of the strip for inducing a change in flux of each said thin magnetic strip independently of said magnetically encoded areas, said change being enhanced or retarded in accordance with the particular magnetic area contiguous to said thin magnetic strip; and sense means normal to said drive associated with said thin magnetic strip in close proximity to said magnetically encoded member for providing a signal proportional to said change in flux; said magnetic strip being anisotropic and having an easy axis of remanent flux orientation defining opposite stable states, and said drive means being adapted to induce a change in flux orientation of each said thin magnetic strip away from said easy axis, said drive winding means being parallel to said easy axis.

Claim 21

A magnetic sensing unit for reading a movable magnetically encoded storage member having a plurality of magnetically encoded areas, comprising: at least one thin magnetic strip adapted to be positioned contiguous to a magnetically encoded area; the plane of the strip being substantially normal to that of the storage member; drive winding means parallel to the easy axis of orientation of the strip for inducing a change in flux of each said thin magnetic strip independently of said magnetically encoded areas, said change being enhanced or retarded in accordance with the particular magnetic area contiguous to said thin magnetic strip; and sense means normal to said drive associated with said thin magnetic strip in close proximity to said magnetically encoded member for providing a signal proportional to said change in flux; said magnetic strip being anisotropic and having an easy axis of remanent flux orientation defining opposite stable states, and said drive means being adapted to induce a change in flux orientation of each said thin magnetic strip away from said easy axis, said drive winding means being parallel to said easy axis.

Claim 22

A magnetic sensing unit for reading a movable magnetically encoded storage member having a plurality of magnetically encoded areas, comprising: at least one thin magnetic strip adapted to be angularly positioned contiguous to a magnetically encoded area; the plane of said thin film being normal to that of said storage member drive means parallel to the easy axis of orientation of said strip magnetically coupled to each said thin magnetic strip for inducing a change in flux in said strip independently of relative movement thereof with respect to said member and nondestructively as to said magnetically encoded areas, said change being enhanced or retarded in accordance with the particular magnetic area contiguous to said thin magnetic strip; and sense means perpendicular to said drive means magnetically coupled to said thin magnetic strip in close proximity to said magnetically encoded member and responsive to said change in flux for providing a signal which is determined by the state of said contiguous magnetically encoded area; said magnetic strip being anisotropic and having an easy axis of remanent flux orientation defining opposite stable states, and said drive means being provided for inducing a change in flux orientation in each said strip.

Claim 23

A magnetic sensing unit for reading a movable magnetically encoded storage member having a plurality of magnetically encoded areas, comprising: at least one thin magnetic strip adapted to be angularly positioned contiguous to a magnetically encoded area; the plane of said thin film being normal to that of said storage member drive means parallel to the easy axis of orientation of said strip magnetically coupled to each said thin magnetic strip for inducing a change in flux in said strip independently of relative movement thereof with respect to said member and nondestructively as to said magnetically encoded areas, said change being enhanced or retarded in accordance with the particular magnetic area contiguous to said thin magnetic strip; and sense means perpendicular to said drive means magnetically coupled to said thin magnetic strip in close proximity to said magnetically encoded member and responsive to said change in flux for providing a signal which is determined by the state of said contiguous magnetically encoded area; said magnetic strip being anisotropic and having an easy axis of remanent flux orientation defining opposite stable states, and said drive means being provided for inducing a change in flux orientation in each said strip.

Claim 24

A magnetic sensing unit for reading a movable magnetically encoded storage member having a plurality of magnetically encoded areas, comprising: at least one planar magnetic strip adapted to be positioned transverse to the direction of movement and in magnetic coupling relationship with one of the magnetically encoded areas of said member; the plane of said strip being normal to that of said storage member; drive means parallel to the easy axis of orientation of said strip magnetically coupled to each said thin magnetic strip for inducing a change in flux in said strip which is affected by the polarity of said magnetically encoded area independently of relative movement thereof with respect to said magnetically encoded member; and sense winding means disposed substantially perpendicular to said drive means and operably associated with said thin magnetic strip for providing a signal, the polarity of which is indicative of the polarity of the coupled magnetically encoded area; said magnetic strip being anisotropic in character and having an easy axis of remanent flux orientation defining opposite stable states and said drive means being adapted to induce a change in flux orientation in each said strip.

Claim 25

A magnetic sensing unit for reading a movable magnetically encoded storage member having a plurality of magnetically encoded areas, comprising: at least one planar magnetic strip adapted to be positioned transverse to the direction of movement and in magnetic coupling relationship with one of the magnetically encoded areas of said member; the plane of said strip being normal to that of said storage member; drive means parallel to the easy axis of orientation of said strip magnetically coupled to each said thin magnetic strip for inducing a change in flux in said strip which is affected by the polarity of said magnetically encoded area independently of relative movement thereof with respect to said magnetically encoded member; and sense winding means disposed substantially perpendicular to said drive means and operably associated with said thin magnetic strip for providing a signal, the polarity of which is indicative of the polarity of the coupled magnetically encoded area; said magnetic strip being anisotropic in character and having an easy axis of remanent flux orientation defining opposite stable states and said drive means being adapted to induce a change in flux orientation in each said strip.

Claim 26

A magnetic reading unit for sensing magnetized members and comprising: support means, at least one thin magnetic strip having a longitudinal axis and supported on said support means such that said longitudinal axis is substantially normal to a magnetically encoded member to be read; drive winding means parallel to the easy axis of orientation of said strip for receiving a current waveform to effect a flux change in each said thin magnetic strip independently of said magnetically encoded member; and a sense winding perpendicular to said drive winding means associated with said thin magnetic strip in close proximity to said magnetically encoded member for providing an output waveform in accordance with said flux change; said magnetic strip being anisotropic in character and having an easy axis of remanent flux orientation defining opposite stable states and said drive means being adapted to effect a change in flux orientation in each said strip away from the easy axis, said easy axis being oriented parallel to the direction of magnetization of said magnetized members.

Claim 27

A magnetic reading unit for sensing magnetized members and comprising: support means, at least one thin magnetic strip having a longitudinal axis and supported on said support means such that said longitudinal axis is substantially normal to a magnetically encoded member to be read; drive winding means parallel to the easy axis of orientation of said strip for receiving a current waveform to effect a flux change in each said thin magnetic strip independently of said magnetically encoded member; and a sense winding perpendicular to said drive winding means associated with said thin magnetic strip in close proximity to said magnetically encoded member for providing an output waveform in accordance with said flux change; said magnetic strip being anisotropic in character and having an easy axis of remanent flux orientation defining opposite stable states and said drive means being adapted to effect a change in flux orientation in each said strip away from the easy axis, said easy axis being oriented parallel to the direction of magnetization of said magnetized members.

Claim 28

A magnetic reading unit for sensing magnetized members and comprising: support means; at least one thin magnetic strip supported oN said support means substantially normal to an area of a magnetically encoded member to be read; drive winding means parallel to the easy axis of orientation of said strip for receiving a current waveform of a magnitude to effect a flux change in said thin magnetic strip independently of said magnetically encoded member and nondestructive as to the magnetically encoded area; and sense winding means disposed normal to said drive winding means and magnetically coupled with said thin magnetic strip and responsive to flux change in said strip for providing an output wave form, the polarity of which is indicative of the polarity of said magnetically encoded area; said magnetic strip being anisotropic in character and having an easy axis of remanent flux orientation defining opposite stable states and said drive means being adapted to effect a change in flux orientation in said magnetic strip with respect to the easy axis thereof, said easy axis being oriented parallel to the direction of magnetization of said magnetized members.

Claim 29

A magnetic reading unit for sensing magnetized members and comprising: support means; at least one thin magnetic strip supported oN said support means substantially normal to an area of a magnetically encoded member to be read; drive winding means parallel to the easy axis of orientation of said strip for receiving a current waveform of a magnitude to effect a flux change in said thin magnetic strip independently of said magnetically encoded member and nondestructive as to the magnetically encoded area; and sense winding means disposed normal to said drive winding means and magnetically coupled with said thin magnetic strip and responsive to flux change in said strip for providing an output wave form, the polarity of which is indicative of the polarity of said magnetically encoded area; said magnetic strip being anisotropic in character and having an easy axis of remanent flux orientation defining opposite stable states and said drive means being adapted to effect a change in flux orientation in said magnetic strip with respect to the easy axis thereof, said easy axis being oriented parallel to the direction of magnetization of said magnetized members.

Claim 30

A magnetic reading head for sensing magnetized members comprising: a thin magnetic strip adapted to be angularly positioned with an edge adjacent a surface of a member to be sensed; the plane of the strip being normal to that of the member being sensed; drive winding means parallel to the easy axis of magnetization of said strip magnetically coupled to said thin magnetic strip near said edge thereof for inducing a change in flux in the portion of said strip near said edge, which is affected by and nondestructive of the magnetization state of said member independently of relative movement therebetween; and sense means disposed perpendicular to said drive winding means and magnetically coupled to said thin magnetic strip in close proximity to said edge of said strip for providing a signal waveform which is determined by the state of said magnetized member; said magnetic strip being anisotropic in character and having an easy axis of remanent flux orientation defining opposite stable states and said drive means being adapted for inducing a change in flux orientation in the strip, said easy axis of magnetization being oriented parallel to the direction of magnetization of said magnetized members.

Claim 31

A magnetic reading head for sensing magnetized members comprising: a thin magnetic strip adapted to be angularly positioned with an edge adjacent a surface of a member to be sensed; the plane of the strip being normal to that of the member being sensed; drive winding means parallel to the easy axis of magnetization of said strip magnetically coupled to said thin magnetic strip near said edge thereof for inducing a change in flux in the portion of said strip near said edge, which is affected by and nondestructive of the magnetization state of said member independently of relative movement therebetween; and sense means disposed perpendicular to said drive winding means and magnetically coupled to said thin magnetic strip in close proximity to said edge of said strip for providing a signal waveform which is determined by the state of said magnetized member; said magnetic strip being anisotropic in character and having an easy axis of remanent flux orientation defining opposite stable states and said drive means being adapted for inducing a change in flux orientation in the strip, said easy axis of magnetization being oriented parallel to the direction of magnetization of said magnetized members.

Claim 32

A magnetic reading head for sensing magnetized members comprising: a thin magnetic strip adapted to be positioned with an edge adjacent a surface of a member to be sensed; with the plane of the strip normal to that of the member to be sensed; drive winding means parallel to the easy axis of orientation magnetically coupled to said thin magnetic strip for inducing a change in flux in said strip, which is affected by the magnetization state of said member independently of relative movement therebetween; and sense means disposed perpendicular to said drive means and coupled with said thin magnetic strip proximate said magnetized member for providing a signal waveform which is determined by flux change in the portion of said strip proximate said edge thereof; said magnetic strip being anisotropic and having an easy axis of remanent flux orientation defining opposite stable states and said drive means being adapted to induce a change in flux orientation with respect to the easy axis of said strip, said easy axis being oriented parallel to the direction of magnetization of said magnetized members.

Claim 33

A magnetic reading head for sensing magnetized members comprising: a thin magnetic strip adapted to be positioned with an edge adjacent a surface of a member to be sensed; with the plane of the strip normal to that of the member to be sensed; drive winding means parallel to the easy axis of orientation magnetically coupled to said thin magnetic strip for inducing a change in flux in said strip, which is affected by the magnetization state of said member independently of relative movement therebetween; and sense means disposed perpendicular to said drive means and coupled with said thin magnetic strip proximate said magnetized member for providing a signal waveform which is determined by flux change in the portion of said strip proximate said edge thereof; said magnetic strip being anisotropic and having an easy axis of remanent flux orientation defining opposite stable states and said drive means being adapted to induce a change in flux orientation with respect to the easy axis of said strip, said easy axis being oriented parallel to the direction of magnetization of said magnetized members.

Claim 34

A magnetic sensing unit for monitoring external magnetic fields comprising: a thin magnetic strip adapted to be positioned at a location to be monitored; the plane of the strip being normal to that of the location to be monitored; drive winding means parallel to the easy axis of orientation of said strip for inducing a change in flux in said thin magnetic strip independently of relative movement of said strip in the field to be monitored, said change being affected by the external magnetic field present at said location; and sense means perpendicular to said drive means magnetically coupleD to said thin magnetic strip for providing an output signal indicative of the presence of an external magnetic field at said location; said magnetic strip being anisotropic in character and having an easy axis of remanent flux orientation defining opposite stable states and said drive means being adapted to induce a change in flux orientation in said strip with respect to the easy axis thereof, said easy axis being oriented parallel to the direction of said external magnetic fields.

Claim 35

A magnetic sensing unit for monitoring external magnetic fields comprising: a thin magnetic strip adapted to be positioned at a location to be monitored; the plane of the strip being normal to that of the location to be monitored; drive winding means parallel to the easy axis of orientation of said strip for inducing a change in flux in said thin magnetic strip independently of relative movement of said strip in the field to be monitored, said change being affected by the external magnetic field present at said location; and sense means perpendicular to said drive means magnetically coupleD to said thin magnetic strip for providing an output signal indicative of the presence of an external magnetic field at said location; said magnetic strip being anisotropic in character and having an easy axis of remanent flux orientation defining opposite stable states and said drive means being adapted to induce a change in flux orientation in said strip with respect to the easy axis thereof, said easy axis being oriented parallel to the direction of said external magnetic fields.

Claim 36

A magnetic sensing unit for monitoring external magnetic fields comprising: a thin magnetic strip adapted to be positioned at a location to be monitored; the plane of the strip being normal to that of the location being monitored; drive winding means parallel to the easy axis of orientation of said strip for inducing a change in flux in said thin magnetic strip independently of relative movement of said strip in the field to be monitored, said change being enhanced or retarded in accordance with the external magnetic field at said location; and sense winding means perpendicular to said drive means and associated with said thin magnetic strip for providing an output waveform, the polarity of which is indicative of the external magnetic field at said location; said magnetic strip being anisotropic and having an easy axis of remanent flux orientation defining opposite stable states, and said drive means being adapted to induce a change in flux orientation in said strip away from the easy axis thereof, said easy axis being oriented parallel to said external magnetic fields.

Claim 37

A magnetic sensing unit for monitoring external magnetic fields comprising: a thin magnetic strip adapted to be positioned at a location to be monitored; the plane of the strip being normal to that of the location being monitored; drive winding means parallel to the easy axis of orientation of said strip for inducing a change in flux in said thin magnetic strip independently of relative movement of said strip in the field to be monitored, said change being enhanced or retarded in accordance with the external magnetic field at said location; and sense winding means perpendicular to said drive means and associated with said thin magnetic strip for providing an output waveform, the polarity of which is indicative of the external magnetic field at said location; said magnetic strip being anisotropic and having an easy axis of remanent flux orientation defining opposite stable states, and said drive means being adapted to induce a change in flux orientation in said strip away from the easy axis thereof, said easy axis being oriented parallel to said external magnetic fields.