This chapter discusses a signal ground to describe a reference plane that is as close to an equipotential plane as is feasible. The voltages appearing between the earth ground–to-neutral connection within a building and earth ground outside of a building will contain AC power and Radio frequencies. The AC neutral is connected to safety ground and earth ground in both services and earth ground carry some of the neutral return current. The sources of electrical codes seldom consider the requirements of instrumentation systems; grounding schemes may be designed that improve signal grounding and that comply with safety regulations. Electrical bonding is a term used for the process of connecting metal structures together in order to achieve a low-resistance contact. Grounding to earth is required for safety, to minimize touch potentials due to AC line leakage or equipment breakdown or direct or indirect lightning strikes, or where a receiving or transmitting antenna uses the earth as a counterfoil.