Before DMX, in the days when multicore analogue systems were prevalent, the console was physically connected on a channel by channel basis to the dimmers. If your console had 24 channels, you had 24 dimmers and channel 1 would always operate dimmer 1. If you wanted to group a set of lights that were spread around the rig on different circuits, you had to perform a "hard patch" where "circuit tails" were plugged into dimmer outputs. These days, now dimmer technology is significantly cheaper, it is more usual that consoles have many more channels than there are dimmers, and each dimmer is physically connected to a single circuit. This means that the console is in charge of the patching.

For example, consider the one-to-one patch diagram below. The two channels are coloured red and blue to distinguish them (obviously a real DMX line can have up to 512 channels). In this diagram, the console has had it's soft patch set to make one channel (i.e. one slider) control one dimmer and it's associated circuit.

Dimmer 1 will have been given the base address of 0 and dimmer 2 will have been given the base address of 1. (There are reasons for starting at zero, but they are not critical to understanding the workings of DMX.) The console will have been set up so that when slider 1 is moved, it sends signals to DMX channel 0 and when slider 2 is moved, it sends signals to DMX channel 1. So, the mappings from console channel to DMX channel to dimmer/circuit are

In a large show, as a simplistic example, you might have an area of the stage lit by five lights that are on circuits 5, 9, 21, 54 and 60. In a one-to-one patch, these circuits would be mapped to their corresponding console channels 5, 9, 21, 54 and 60. When you come to programme scenes into the esk, it is often nice to have the lights for areas on adjacent sliders, say 1, 2, 3, 4 and 5. The DMX soft patch system allows you to do this because the one-to-one patch is not hardwired as it would be in an analogue multicore system. Using the software in the console, it is possible (and desirable) to set the above group up as follows:

It now appears to the console operator that the lights are connected to channels 1-5, when in reality they are spread out all over the channel map.

This opens up further possibilities because console channels can be set up on a many to one mapping as shown below:

In this situation, the console has been configured so that a single slider (slider 1 here) controls the DMX for both circuit 1 and 2 such that when slider 1 is moved, the change is reflected in both circuits simultaneously. To do this in the old analogue scheme of things, both circuits 1 and 2 would have needed to be connected to a single dimmer on a "Patch Board". This also increases the risk of dimmer overloading, whereas the new dimmer per circuit system makes this much less likely.