|  | 8.6 | Planning Structured Cabling: Electricity and Grounding
| 8.6.2 | AC line noise
After it reaches our homes, schools, and offices, electricity is carried to appliances and machines via wires concealed in walls, floors, and ceilings. Consequently, inside these buildings AC power line noise is all around us. If not properly addressed, power line noise can present problems for a network. In fact, you will discover as you work with networks, that AC line noise, coming from a nearby video monitor, or hard disk drive, can be enough to create errors in a computer system. It does this by adding unwanted voltages to the desired signals and preventing a computer's logic gates from detecting the leading and trailing edges of the square signal waves. This problem can be further compounded when a computer has a poor ground connection.