MoniSwitch ADB: A KVM for ADB Macs

Sometimes you just have more Macs than monitors – or wish you could free up some space in your network center. But you need a keyboard and mouse to run your Macs, and a monitor to see what you’re doing.


One time-tested solution is Timbuktu (Netopia, $149 per user, less in quantity), a program that lets you completely control a Mac remotely. Your mouse and keyboard act as the mouse and keyboard of the remote Mac. Your monitor displays what its monitor would show. In fact, Timbuktu has made running headless servers (no monitor) viable – and common in some shops.

The drawbacks: Most Macs power up from a power key on an attached keyboard, you need at least a mouse to make any changes to the remote Mac when it has problems that prevent use of Timbuktu, and you’ll need to tote a monitor around when running diagnostics and other things that can’t be done remotely.

On top of that, you’re limited by the speed of your connection to the other Mac. If you’re on 100Base-T ethernet, that’s not a big issue. On 10Mbps ethernet, it’s poky, but you can live with it. On LocalTalk, it’s a lesson in patience. Via modem, it can be very frustrating.

But it works. Timbuktu is a viable product even with slow connections.

What About a Switch Box?

Because you need a monitor, mouse, and keyboard attached to a server some of the time – but probably not all of the time – there has been a small market for switches that let you connect several Macs to one ADB port (for mouse and keyboard) and one monitor. Many are electronic. Until now, all have been very expensive.

MoniSwitch2, frontEnter Dr Bott, a German distributor of Macintosh related products. They learned the ins and outs of ADB and Macintosh video, then designed their MoniSwitch2 and MoniSwitch4 to work perfectly with them. Video isn’t a real problem – as long as the Mac sees a monitor at startup, it assumes it’s still connected, whether you turn it off or remove it.

ADB is another story, since it lets the Mac know you have a keyboard and mouse attached. The MoniSwitch has to work in such a way that switching the ADB chain to another computer and then back doesn’t reset your Mac or send some unwanted command.

The MoniSwitch does this perfectly.

What Is MoniSwitch?

The MoniSwitch comes in two-way and four-way configurations. According to Dr Bott KG, you can even chain them together.

MoniSwitch2, rearOn the back of the MoniSwitch are three or five ADB and DA-15 video ports. Two or four for connection to your Macs, one for your monitor, mouse, and keyboard.

Remarkably, considering the price (US$105 for the MoniSwitch2, US$160 for the MoniSwitch 4*), the MoniSwitch comes with all the video and ADB cables you need to connect to your Mac. You could easily pay $160 for four video and ADB cables, but here you get the switch as well.

The cables are of excellent quality. With two MoniSwitch4 in use, I only see the least bit of ghosting when driving a Sony Multiscan 500PS monitor at 1280 x 1024. The other three attached Macs, working at 640 x 480, show no ghosting at all, nor do the four others connected to an old Radius full page monitor.

The only complaint is that the 1m (3.3′) video cables are a bit short, while the 1.8m (6′) ADB cables are more than long enough. [Update: In January 1999, Dr. Bott began shipping 2m/6.6′ cables for both ADB and monitors.] It can take a bit of work to arrange four computers so their video ports are within 3.3′ of the switch. I’d be willing to pay a bit more for 1.2m, 1.5m, or even 1.8m video cables and hope Dr Bott considers packages where the video and ADB cables are more closely matched in length – and at least 4′ (1.2m) long.

(Dr Bott stocks other lengths and will even custom manufacture cables, but at a fairly steep price. Your local dealer may also be able to help here. Be sure to specify that you need “no shadow” video cables to prevent ghosting.)

Fortunately, it’s very easy to figure out how to connect the MoniSwitch, because all documentation is in German. (English documentation is in the works.)

In use, there’s a brief delay as you switch from computer to computer, maybe one or two seconds. The screen quickly settles down, and the ADB line goes live.

The only problem I’ve had with the MoniSwitch comes when I move the mouse too soon after switching, which sometimes locks up the Apple Desktop Bus. Dr Bott KG kindly supplies ADB Renewer** to reset the bus. On the up side, it works. On the down side, you have to plan ahead to launch a program with your mouse disabled.

My solution is to use QuicKeys to launch ADB Renewer from the keyboard. It may take a few seconds for your Mac to recognize and respond to the keystroke, but ADB Renewer will come up just long enough to reset ADB, then quit.

The other reason you’ll want ADB Renewer on your Mac is that you might have different mouse tracking settings on different computers. Sometimes you lose that setting; ADB Renewer brings it back.

I justified the cost of the MoniSwitch4 in terms of the number of keyboards and monitors it would free for other uses. In one area, I had four Macs, four monitors, four mice, and four keyboards. This took up an incredible amount of space – and the servers are usually started and simply left running. With the MoniSwitch4 sitting between them, four Macs are controlled by a single mouse and keyboard and displaying video on a single monitor.

In my office I have five Macs, four in one area and a backup server on the other side. I’d had three Macs stacked with keyboards and mice stacked around them, a 12″ Apple Monochrome Display connected to the video port of whichever I needed to work with. And so often I’d grab the wrong keyboard….

With MoniSwitch, I simply turn a knob to control my work computer, a web/mail server, a list server, and a test machine. Very nice.

What About Timbuktu?

None of this obviates the importance of Timbuktu for remote control. The farther away the other Macs, the more useful Timbuktu is.

But if you have a cluster of Macs, they each need occasional access to a mouse, keyboard, and screen. For about the price of a decent used color monitor, you can buy a MoniSwitch – and reduce clutter at the same time.

Another benefit of the MoniSwitch is that there’s no delay while your computer is controlling another one. Instead, you’re directly controlling the Mac with a connected keyboard and mouse.

Where Can I Get a MoniSwitch?

You can order directly from Dr Bott, but shipping from Germany is not cheap (assuming you’re in North America – for European readers, I’m sure it’s quite a different situation). [Update: There is no longer a North American distributor. You can order the MoniSwitch4/ADB-40, as it’s now called, from Dr Bott for 99.99€ plus shipping.]

You may have a local dealer who is working with Dr Bott or a distributor, although dealers are few and far between in the U.S.

A third alternative is Dr. Bott LLC, the official U.S. and Canada distributor. You can order direct or work through your local Apple dealer. [Update: Dr Bott LLC, the North American distributor, filed for bankruptcy and went out of business in 2014. Dr Bott remains in business in Europe and continues to sell the 4-way MoniSwitch4 for ADB.]

updated MoniSwitch ADBThere’s also a MoniSwitch USB.

* Prices subject to change based on the exchange rate between the German Mark and the American Dollar.
** ADB Renewer is being replaced with ADB Cleaner, a functionally identical program.

1999.12.21: Dr. Bott has announced a new MoniSwitch ADB (right) with the same styling as the MoniSwitch USB.

2016.08.02: Dr Bott currently has a wide range of MoniSwitch devices available:

  • MoniSwitch4/ADB-40, 99.95€
  • MoniSwtich2/USB-02, 99.00€
  • MoniSwitch4/USB-04, 125.00€
  • MoniSwitch/2 DVI XGA with USB, 79.95€
  • MoniSwitch/4 DVI XGA with USB, 99.95€
  • MoniSwitch mini DL, mac mini size and style, supports 2 Macs, 199.00€
  • MoniSwitch Pro DVI DL, supports dual-link displays, 4 Macs, 399.00€
  • MoniSwitch Pro Dual VGA, supports 4 Macs with USB and 2 VGA monitors, $199.00€

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