Electrical chassis ground

Chassis groimd A connection to the metal frame of an electronic system that holds the components in a place. The chassis ground connection serves as the ground return or electrical common for the system. 

Most modern electronic instruments have a cord that contains a separate ground wire for the chassis and are supplied with a suitable fuse or other overload protection. Any existing instrument that lacks these features should be modified to incorporate them. As is true for any electrical equipment, special precautions should be taken to avoid the possibility that water or other chemicals could be spilled into these instruments. 

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