Abstract: An electric current detector which is mountable on a circuit board on which there is mounted a fluxgate-type magnetic sensor IC chip which detects magnetic flux for electric current detection, including: a substantially ring-shaped core which forms a magnetic-path for magnetic flux induced by detection-target electric current, wherein the core includes a gap which is arranged to become substantially parallel with respect to the circuit board when mounting the aforesaid electric current detector on the circuit board and which is at a place positioned on or on the upper side of the magnetic sensor IC chip in the magnetic-path when mounting the aforesaid electric current detector on the circuit board.

Abstract: An electric current detector which is mountable on a circuit board on which there is mounted a fluxgate-type magnetic sensor IC chip which detects magnetic flux for electric current detection, including: a substantially ring-shaped core which forms a magnetic-path for magnetic flux induced by detection-target electric current, wherein the core includes a gap which is arranged to become substantially parallel with respect to the circuit board when mounting the aforesaid electric current detector on the circuit board and which is at a place positioned on or on the upper side of the magnetic sensor IC chip in the magnetic-path when mounting the aforesaid electric current detector on the circuit board.

Abstract: A contactless power supply system includes a power transmission coil, a power receiving coil, and a center tap that is provided at the power transmission coil. Specifically, the power transmission coil has a first coil and a second coil. The first coil is configured with a first conducting wire that circularly extends from the center tap by winding in a first direction from a first internal circumference side to a first external circumference side. The second coil is configured with a second conducting wire that circularly extends from the center tap by winding in a second direction, which is opposite to the first direction, from a second internal circumference side to a second external circumference side. A first number of windings of the first coil is approximately the same as a second number of windings of the second coil.

Abstract: A wireless communication system may include a first coil having at least a function of transmitting signal information, a relay coil, and a second coil having at least a function of receiving the signal information, and satisfying Equation (1): RO1>RO2>RO3, where RO1 represents an outer diameter of the first coil, RO2 represents an outer diameter of the relay coil, and RO3 represents an outer diameter of the second coil, and a small portable device, a housing case for a small portable device, and a communication device for a small portable device to be used in the wireless communication system.

Abstract: A coil is formed by coaxially winding a second winding so as to be in intimate contact with an outer circumferential portion of a first winding wound about a winding shaft axis. In the first winding, one side of a winding wire is wound from an inner circumferential side to an outer circumferential side, the other side of the winding wire is drawn forth from the inner circumferential side to the outer circumferential side, while crossing the one side of the winding wire, and a thickness in a direction of the winding shaft axis in crossing portions of the one side of the winding wire and the other side of the winding wire is equal to a thickness in other portions.

Abstract: A coil is formed by coaxially winding a second winding so as to be in intimate contact with an outer circumferential portion of a first winding wound about a winding shaft axis. In the first winding, one side of a winding wire is wound from an inner circumferential side to an outer circumferential side, the other side of the winding wire is drawn forth from the inner circumferential side to the outer circumferential side, while crossing the one side of the winding wire, and a thickness in a direction of the winding shaft axis in crossing portions of the one side of the winding wire and the other side of the winding wire is equal to a thickness in other portions.