What is a former wound coil?

A former wound coil is a type of electrical coil in which the wire that forms the coil is wound around a former, which is a cylindrical or semi-cylindrical object. The former can be made of various materials, such as plastic or ceramic. The wire is typically coated with an insulating material, such as enamel, to prevent the coil from shorting out. Former wound coils are often used in high-frequency and radio applications, where they are required to withstand high levels of electromagnetic interference.