Classes of USB KVM Switches

With the popularity of USB; USB keyboards, mice and I/O devices are still the most common devices connected to a KVM switch. The classes of KVM switches reviewed are based on different types of core technologies in terms of the KVM switch handling USB I/O devices--including keyboard, mouse, touch screen display, etc. (USB HID class devices- Human Interface Devices ).
1. USB HUB based KVM

Also called Enumerated USB KVM switch. A connected/shared USB device is required for the full initiation process (USB enumeration) EVERY TIME the KVM is switched to another target system/port. The switching to different ports is just as if you were to physically plug and unplug a USB device into your targeted system.

2. Emulated USB KVM

Dedicated USB console port(s) are assigned to emulate special sets of USB keyboard or mouse switching control information to each connected/targeted system. Emulated USB provides an instantaneous and reliable switching action that makes keyboard hotkey and mouse switching possible. However, this class of KVM switches uses only generic emulations and consequently have only been able to support the most basic keyboard and mouse features.

3. Semi-DDM USB KVM

Dedicated USB DDM console port(s) work with all USB HID devices (including keyboard and mouse), but do not maintain the connected devices' presence to all the targeted systems simultaneously. This class of KVM switch takes advantage of DDM (Dynamic Device Mapping/ True Emulation ) technology to quickly enumerate the first connected system and keep the enumeration to the console side of the KVM switch for the next switching action to the other connected systems. It is only DDM to the console side but not to every connected system (of the PC side connections).

4. DDM USB KVM or True Emulation KVM

Dedicated USB DDM console port(s) work with all USB HID devices (including keyboard and mouse) and maintain the connected devices’ special functions and characteristic to each connected/targeted systems. This class of KVM switches overcomes the frustrating limitations of an Emulated USB Class KVM by emulating the true characters of the connected devices to all the computers simultaneously. This means that you can now use the extra function keys, wheels, buttons, and controls that are commonly found on modern keyboards and mice.

Comparison - Classes of USB KVM Switches