The TRENDNet TK-IP101 is a small unit; not much more than 8-inches long and barely 3/4 of an inch high. On the front of the TK-IP101 TRENDNet has put two PS/2 ports as well as a serial console RJ-11 port. Also on the front are four indicator lights; these let you know if you have any issues with connectivity and include, link, 10/100 LAN connection, video and power.
Flipping around to the back, you have the rest of your connections including VGA (for up to 1600x1200 resolutions), LAN (10/100), serial for power and other functions, and an output for your PC or to a bridge KVM. One other port of interest is the USB port. On paper this is to allow you to connect to a USB KVM or to connect to a PC via USB.
While I was able to connect to a single Windows PC using USB, I was never able to get this to work with the USB capable TK-423K. The keyboard and mouse indicated they had power, but would not respond on any connected PC.
A power port is located along the right side of the TK-IP101.
The four-port TK-423K is a much larger device; measuring almost 12-inches in length and roughly 2.5-inches in height. It has four buttons across the front with red LEDs next to them; these are for the individual systems. The selected system will light up solid red if it is on and connected properly. If the system is off or there is a problem with the connection, it will blink red.
The back side of the TK-423K is the business end; here you have all of your connectivity.
There are four system connection banks for your systems. These include a single connection for KVM out as well as audio (mic and stereo speakers). For input to the systems you have options for PS/2 or USB keyboards and mice, stereo speaker and mic inputs and VGA monitor out with supported resolutions of up to 2048x1536, which is pretty impressive for a VGA only KVM.