It is important to first review some of the key terms used by engineers to describe various reed products. The next two slides define the terms used in this training module. A bias or permanent magnet is a steady magnetic field applied to the magnetic circuit of a relay or sensor to aid or impede operation of the contacts. An electromagnetic assembly consisting of one or more windings of copper insulated wire usually wound on a bobbin or spool is a coil. When current is applied to the coil, a magnetic field is generated, operating the contacts of a Reed Relay or Electromechanical Relay. De-energize is the act of removing power from a relay coil, while energization is the application of power to the relay coil.