The JustCom JC-104A is a 4-port VGA PS/2 KVM switch with audio support. As of this writing, it appears to be the only KVM switch on the market which can deal with audio in even a semi-intelligent manner. Overall it is a good switch, but I have experienced a few problems.

Specifications

The unit measures 6.3w x 3.8d x 1.7h inches (160w x 96d x 43h mm). The case appears to be made entirely out of metal, and is quite heavy for its size. The back and sides are painted black, and the front is brushed bare metal. It comes with a plastic stand which allows the switch to be placed in either a horizontal or vertical position.

The back of the unit has a port for a monitor cable, a port for a 1/8" (3.5mm) stereo speaker cable, a power adapter port, and four ports for proprietary 5-in-1 cables (one for each attached CPU). The front of the unit has four buttons for selecting the active CPU; indicator lights showing whether each port is selected (green), available (red) or unavailable (none); and connectors for a 1/8" (3.5mm) stereo speaker cable, a 1/8" (3.5mm) mono microphone cable, a PS/2 keyboard cable, and a PS/2 mouse cable.

The package also includes two 4-foot 5-in-1 cables, two 6-foot 5-in-1 cables, a power adapter (9VDC, 600mA) and a user manual.

Electrically, the JC-104A is an FCC Class B and CE Class B device, therefore it may cause radio interference, but I have not experienced any interference problems from it.

The proprietary 5-in-1 cables carry the keyboard, video, mouse, speaker and microphone signals though a single cable. The individual connectors which connect to the CPU emerge from the VGA connector at the computer end. These short CPU-end cables are about 12 inches long. The 5-in-1 section of each cable appears to comply with the IEEE 2919 specification and connects to the switch using DB26 connectors.

Features

Independently switchable audio -- Perhaps the one feature which makes this switch unique is the ability to select one CPU for the keyboard, video, and mouse, while selecting a different CPU for the speakers and microphone. Effectively, this allows you to use one computer, while listening to another. To use this feature, you must use hot key sequences; the buttons on the front panel always switch all functions to the new CPU. It would have been better if it were possible to listen to all computers simultaneously (through audio mixing), and broadcast the microphone signal to all computers simultaneously, but as of this writing, no switch on the market appears to be able to do that. The JC-104A's independently switchable audio may be the best option available at the present time.

PS/2 mouse/keyboard emulation -- The JC-104A performs PS/2 emulation on both the keyboard and mouse ports. This allows a computer to boot correctly, even if it is not currently selected on the switch. Like most other KVM switches, this is accomplished by simulating a generic wheel mouse. My experience has been that this feature works correctly nearly all the time. There is, however, a short period during the BIOS phase of the boot sequence where, if the selected CPU is changed on the switch, the booting computer may not detect the mouse properly.

Keyboard state restoration -- The materials related to the switch claim that it restores the state of keyboard lights to the values associated with the selected computer. My experience has been that this feature does not work at all. When a new CPU is selected, the lights seem to be turned on/off in a seemingly random manner.

Video quality -- The materials related to the switch state that it can support resolutions up to 2048 x 1536 @ 85Hz; however, JustCom technical support was not able to provide me with an exact dot-clock video bandwidth figure. Nonetheless, I can say that the picture quality on my 1280 x 1024 @ 60Hz display is as good as if the monitor were connected directly to the computer. There is no noticeable blurring, ghosting or color-shifting.

Hot keys -- The JC-104A is able to switch between CPUs using key sequences. Like most KVM switches, the sequences start with two presses of the Scroll Lock key. The key sequences allow cycling through CPUs in sequence, or selecting an individual CPU. Furthermore, key sequences also allow the CPU used for the keyboard, video and mouse to be changed without changing the CPU used for audio, and vice versa. Additional key sequences are used to enable/disable auto-scan mode, change the auto-scan time and turn the buzzer on and off.

Regarding hot keys, first, the switch does not always recognize the double Scroll Lock sequence, so in order to ensure that it works properly, you need to press the Scroll Lock key three times. Second, some of the actual key sequences are non-intuitive. I can somewhat understand why "P" changes the keyboard, video and mouse CPU (perhaps it refers to "picture" or "PS/2"), but I can never remember that "V" changes the speaker and microphone CPU (the best I can come up with is "voice" as a mnemonic for this one).

Auto-scan mode -- This cycles through all of the connected CPUs at an interval of 3, 5, or 7 seconds, depending on the settings. The scan stops when you hit the space bar. This seems to work just fine.

Other Experiences

One problem with the JC-104A is that the speaker, microphone, keyboard and mouse connectors are in the front of the unit. This means that the unit may need to be recessed about 1.5 inches from where you otherwise might want it to be. It also means that you may need a cable management strategy to get the cables as much out of the way as is possible.

Occasionally, while switching CPUs, I have noticed that the mouse will become erratic. When this happens, there does not appear to be a way to restore proper mouse function without rebooting the affected computer. While this is an annoyance, in the three months I have had my JC-104A, this has only happened about 10 times, so it isn't a huge problem. Also, the only computer which seems to be affected is a Windows 95 computer with a 1999 motherboard. Newer machines do not seem to have this problem.

The unit appears to be hot-pluggable. In other words, computers can be added or removed from the switch without disrupting other computers, or interfering with switch operation.

The JC-104A does not support plug-and-play monitors. Monitors which support plug-and-play will still work fine, but when configuring a computer's video settings, you will either have to plug the monitor directly into the computer, or you will have to adjust the settings completely manually.

The "buzzer" (JustCom's word) on the JC-104A actually produces a quiet beep. The beep is quiet enough that it is not at all disturbing. However, if you like, there is a hot key sequence to disable it completely.

The unit can operate with or without the power adapter. The switch supplies enough power to the mouse port to support my optical mouse, even without the power adapter. Without the power adapter, the power appears to be drawn from the PS/2 keyboard ports of any connected CPUs. (The presence of power on the PS/2 keyboard port also appears to be the way the switch detects the presence of a computer connected to the switch.)

When using the buttons on the front of the unit to switch between CPUs, all functions (KVM and audio) are switched. Unfortunately there are not separate buttons for switching just KVM or just audio. This means that if you want to switch the KVM function while keeping the audio the same, you have to use the hot key sequence.

Conclusion
Overall, I am happy with this switch. It does have its idiosyncrasies which require some getting used to, and it does occasionally do something completely wrong, but it still may be one of the best switches currently on the market.

Recommended: Yes

Amount Paid (US$): 58
Driver Availability: Other