For shorter cable runs of 25 meters or less, Gigabit Ethernet will allow transmission over a special balanced 150 ohm cable.  This is a new type of shielded cable; it is not UTP or IBM Type I or II.  In order to minimize safety and interference concerns caused by voltage difference, both transmitters and receivers will share a common ground.  The return loss for each connector is limited to 20db to minimize transmission distortions.  The connector type for 1000Base-CX will be a DB-9 connector.  A new connector is being developed by AMP called the HSSDC, which will be included in the next revision of the draft.

The application for this type of cabling will be short-haul data-center interconnections and inter-rack connections. Because of the distance limitation of 25 meters, this cable will not work for interconnecting data centers to riser closets.

See also, 1000BaseT, 1000BaseSX  and 1000BaseLX.