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A perforating assembly includes a material that can respond to a magnetic field by changing shape multiple times and causing a fire control circuit to activate and deactivate. The material may be a magnetic shape-memory alloy and can change shape when the magnetic field is removed or inverted. When

A perforating assembly includes a material that can respond to a magnetic field by changing shape multiple times and causing a fire control circuit to activate and deactivate. The material may be a magnetic shape-memory alloy and can change shape when the magnetic field is removed or inverted. When the material changes shape, the material can cause another component of the perforating assembly to change position to activate or deactivate the fire control circuit, as desired.

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1. A perforating assembly positionable in a wellbore traversing a subterranean formation, the perforating assembly comprising: a fire control circuit;a material adapted to change shape multiple times in response to a magnetic field for causing the fire control circuit to activate and deactivate, the

1. A perforating assembly positionable in a wellbore traversing a subterranean formation, the perforating assembly comprising: a fire control circuit;a material adapted to change shape multiple times in response to a magnetic field for causing the fire control circuit to activate and deactivate, the material being a magnetic shape-memory alloy;a housing in which is defined a chamber, wherein the fire control circuit is located in the chamber, the fire control circuit comprising an upper portion and a lower portion; anda control device located in the chamber between the upper portion and the lower portion, the control device comprising the material. 2. The perforating assembly of claim 1, wherein the perforating assembly is a tubing conveyed perforating gun. 3. The perforating assembly of claim 1, wherein the magnetic field is proximate to a wellhead of the wellbore. 4. The perforating assembly of claim 1, wherein the material is adapted to change shape in response to the magnetic field that is from a stationary device. 5. The perforating assembly of claim 1, wherein the fire control circuit is an initiator mechanism or a propagation mechanism for a charge in the perforating assembly. 6. The perforating assembly of claim 1, wherein the control device comprises: a control device housing comprising a body and a housing cap that cooperate to define a device chamber;a contact element in the device chamber and extending through the housing cap; anda spring in the device chamber, the spring being adapted for biasing the contact element, wherein the material is in the device chamber between an end of the contact element and a bottom portion of the body. 7. The perforating assembly of claim 1, wherein the fire control circuit in an activated configuration is adapted for allowing a signal or command to cause a charge in the perforating assembly to explode, wherein the fire control circuit in a deactivated configuration is adapted for preventing the signal or command from causing the charge to explode. 8. A control device for a perforating assembly that is positionable in a wellbore traversing a subterranean formation, the control device comprising: a non-magnetic housing comprising a body and a housing cap that cooperate to define a device chamber;a contact element partially in the device chamber and extending through the housing cap; anda material in the device chamber, the material being adapted to change shape multiple times for causing the control device to activate and deactivate the perforating assembly in response to a magnetic field by causing a change in position of the contact element,wherein the control device is located with a fire control circuit in a chamber, the fire control circuit includes an upper portion and a lower portion, the chamber being defined by a housing, the control device being located in the chamber between the upper portion and the lower portion. 9. The control device of claim 8, wherein the material comprises a magnetic shape-memory alloy. 10. The control device of claim 8, wherein the magnetic field is proximate to a wellhead of the wellbore. 11. The control device of claim 8, wherein the contact element in an activation configuration of the control device is adapted to extend outside the housing cap, wherein the contact element extended outside the housing cap is configured for linking the upper portion to the lower portion of the fire control circuit for allowing a signal or command to cause a charge to explode. 12. The control device of claim 11, wherein the contact element in a deactivation configuration of the control device is adapted to extend through and within the housing cap, wherein the contact element extending within the housing cap is configured for allowing a gap between the upper portion and the lower portion of the fire control circuit for preventing the signal or command from causing the charge to explode. 13. The control device of claim 8, further comprising: a spring in the chamber, the spring being configured for biasing the contact element. 14. The control device of claim 13, wherein the material is adapted to cause the control device to activate by expanding and causing the contact element to overcome a biasing force of the spring and to extend outside of the housing cap, wherein the material is adapted to cause the control device to deactivate by reducing in size and allowing the spring to bias the contact element in a direction that is away from the housing cap. 15. A well system, comprising: a wellhead for a wellbore traversing a subterranean formation;a source of a magnetic field proximate to the wellhead; anda perforating assembly positionable in the wellbore, the perforating assembly comprising: a fire control circuit;a material adapted to change shape multiple times for causing the perforating assembly to activate and deactivate in response to the magnetic field from the source;a housing in which is defined a chamber, wherein the fire control circuit is located in the chamber, the fire control circuit comprising an upper portion and a lower portion; anda control device located in the chamber between the upper portion and the lower portion, the control device comprising the material. 16. The well system of claim 15, wherein the material comprises a magnetic shape-memory alloy, wherein the perforating assembly is a tubing conveyed perforating gun. 17. The well system of claim 15, wherein the control device comprises: a control device housing comprising a body and a housing cap that cooperate to define a device chamber;a contact element in the device chamber and extending through the housing cap; anda spring in the device chamber, the spring being adapted for biasing the contact element,the material in the device chamber between an end of the contact element and a bottom portion of the body. 18. The well system of claim 15, wherein the source of the magnetic field is within ten feet of the wellhead.