Ferranti-Packard Flip Dot Display  
Written by AnubisTTP on 2010-06-01  


Flip dot displays are another 'flap' based electromechanical display in the same family as the vane and flap displays shown above. A flip dot display uses an array of magnetic disks suspended above a matrix of coils to display alphanumeric data. Each coil has a U-shaped bar passing through it, which stores the magnetic state imparted when an electric current passes through the coil. The U-bars are connected to the pivot points of each magnetic disk, causing the disks to flip to match the magnetic state of the bars. Much like core memory, the U-bars store a magnetic state even when power is removed, allowing images to be loaded and stored in the display without any external latches or secondary memory hardware.

This Ferranti-Packard model is made up of an array of five separate flip dot 'bars' each containing seven dots. The coils operate at 5V, and are attached to a diode matrix that prevents a pulse on a given row from inadvertently flipping adjacent dots.


Ferranti Packard flip-dot display, displaying the numeric character "3".

Flip dot displays are a sort of direct view core memory, with U-shaped metal rods that store a binary value magnetically.

The state of each stored bit is indicated by a freely rotating disk on the front of each coil.

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