PVD (Para Visual Display).
On the B747-400 I flew we had a PVD display, (a black and white barbers pole), on the coaming, centrally in front of each pilot.
The PVD requires a useable ILS localiser signal that has to be selected prior to take off. When the aircraft is on and pointing down the runway centreline the display will be stationary.
During the take-off roll, the PVD will provide centreline guidance when the aeroplane exceeds 2.5 degrees or greater deviation from the runway centreline. The display moving to the left is a command to turn to the left and vice versa, the faster the display moves the larger is the command.
This equipment allowed to take off when the RVR was down to, but not, below 100 meters.