When you are thinking of quantity about receiving card, I am sure of that you are going to compare sorts of brand and make a decision later, and before your determination, we need to make a calculation first, that is you will have to calculate the maximum loading capacity of each receiving card you picked already, it means generally each single card has different capacity of signal loading, what's more, the two factors length and width to be considered are totally different from card to card to receive the signal and handling with it, the length and width defined here is related to the pixel dots rather than measurement in horizontal or vertical distance, we can conclude this view is linked to the accurate configuration for receiving card. Usually we will introduce two brands of receiving card NovaStar & Mooncell, the basic resolution for each is 256*226, 512*256, and both of them could load different maximum pixel dots, scan mode will be initiated and the card is fully loaded according to the rule of resolution, static status of LED display is defined as sleeping control mode with the different number of pixel dots loading, however, you have to notice the loading capacity of receiving card is larger than the display pixels of screen, otherwise some display loss will appear on the screen.
Second issue we are going to talk about is the typical synchronous transmission, there is another saying of we call the receiving card as synchronous receiving card, which is ready to connect to computer.
Synchronous card: signal channel link to computer's processing.  It will send the video signal playing on PC to the LED display screen at the same time, in another meaning, you can see the same image scenes playing both on the PC screen and LED display screen. Sending card's maximum loading capacity is measured by formula, 1280 * 1024, maximum loading pixels about one receiving card is half of the sending card, 1280 * 512. So we can conclude that you have to add another receiving card more if the width or length(we talked above) of display is larger than the common unit of 1280 * 512.
Linking method: GPU supports DVI interface, this unit will be installed into AGP slot on the PC's motherboard. Sending card will be inserted to PCI slot then, both of sending card and receiving card will be installed into LED display screen. You'll be able to get them combined via ethernet cables.
Transmission: 100 meters for general ethernet port 
Multi-channel optic fiber: 500 meters
Single-channel optic fiber: 10 kilometers
Advantage: Content storage is depending on PC's disk capacity, easy to edit and fix for display, support animation and mobile media's recap, also support television.
Disadvantage: LED display screen has to work complying with the computer's running, it means the ultra cost for another computer will be added. 
Suggestion: LED display screen is recommended to apply for the synchronous cards if screen size is larger than 3sqm.