The spool is fitted onto a spool holder to guide the spool while in use.

The coil (CL2) is disposed above the coil (CL1), and the coil (CL2) and the coil (CL1) are magnetically coupled to each other.

The antenna coil can be an axial coil or a tilted coil.

The primary coil includes at least one butterfly coil.

The coil (L1) and the coil (L2) together form a common mode choke coil.

The coil includes a first coil section and a second coil section.

A coil component is provided with a primary coil, and a first secondary coil and a second secondary coil facing the primary coil.

The coil may be formed of a coil wire that is polymer coated prior to winding the coil.

The coil (311a) is a solenoid coil.

The excitation coil and the pick-up coil are implemented using a common coil (35) instead of using separate coils for the excitation coil and the pick-up coil.

The reel has a reel width Dw and a reel diameter Dd.

The first coil (30) and the second coil (32) are connected in series to the fundamental coil (28), and the first coil (30) and the second coil (32) are parallelly connected to each other.

A standard coil layer having the standard coil and a small coil layer having the small coil are stacked in such a way that the aperture of the small coil lies within the aperture of the standard coil.

One of the coils from among the primary coil (14) and the secondary coil (27) is a small coil while the other is a large coil.

The supply spool is contained in the supply spool enclosure, and the take-up spool is contained in the take-up spool enclosure.