Isolation / Distribution Transformers have primary and secondary windings are physically separated from each other. The windings of isolation transformer are insulated from each other and are referred to as "insulated". In an isolation transformer the output winding will be isolated. Secondary neutral to ground bonding eliminates common mode noise, providing an isolated neutral-ground reference for sensitive equipment. An isolation transformer allows an AC signal or power to be taken from one device and fed into another without electrically connecting the two circuits. Isolation transformers block transmission of DC signals from one circuit to the other, but allow AC signals to pass. They also block interference caused by ground loops. Isolation transformers are different from auto transformers in which the primary and secondary share a common winding. Isolation transformers are often used to protect high gain circuits, or prevent noisy ground paths in instrumentation.