How to identify different classes of KVM switches

If your KVM switch does not allow you to switch ports/channels by hitting the hot-key combinations, then you have a "HUB class" KVM switch.

For the "Emulated KVM Switch class,” you’ll find that there is a specifically assigned USB port that you can plug your keyboard into for the hot-key commands.

For both "Semi-DDM class" and "DDM class" KVM switches, there is no difference in which DDM port you can plug your keyboard into for the hot-key commands. As long as you plug in the keyboard or the wireless USB dongle to one of the DDM ports (normally there are at least two DDM ports/ KVM switch) you will have hot-key commands. Most importantly, you could have up to two connected keyboards (one for each DDM port) and the hot-key commands would work on both keyboards between all of the connected systems.

The difference between "Semi-DDM" and "DDM" KVM switches are:

1. Semi-DDM switches still cause delays (but very short) when switching between different ports.  However, the DDM switch will have no latency (no delay) in switching between ports/channels.
2. Semi-DDM switches are cheaper in cost since there are no DDM chips within each port/channel of the KVM switch.  For the DDM switch, each channel is equipped with a DDM chip (at least two extra DDM chips per port/channel). That is the main reason why “True DDM” KVM switches cost much more than all other classes of KVM switches.