This article originally appeared in TidBITS on 1991-09-23 at 12:00 p.m.
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TelePort Capabilities

by Mark H. Anbinder

The coolest Macintosh telecommunications gadget is the TelePort modem from Global Village Communications. Global Village has created a small, unobtrusive modem that doesn't need a power cord and won't even take up one of your serial ports. It's a 2400 bps modem, complete with MNP capabilities through level 5 for error correction and data compression. There's even a 9600 bps fax version that lets you send faxes right from your computer (fax receiving has not been implemented in the current crop of TelePorts).

An Apple Desktop Bus (ADB) device, the TelePort plugs into the computer the same way your keyboard, mouse, or trackball does, at least on the Macintosh SE or later. Either the spare ADB port on the back of your computer or the one on the side of your keyboard will work fine. For computers with only one ADB port, like the Macintosh Classic, LC, or IIsi, the TelePort comes with an ADB "Y-splitter" that lets you connect two devices to one port.

Not only does the TelePort communicate with the computer through the rarely-used ADB channel, it also takes its electrical power from the ADB. While the ADB normally provides power and communications only to the keyboard and mouse, Apple originally intended it to support other devices from third-party developers. Other than keyboards and mice or mouse-replacements, the TelePort is the first. The TelePort should work just fine with any other ADB devices that come to market, though the ADB could be overtaxed by too many devices talking at once. At worst, this would slow down communications a bit.

Because the TelePort is a Communications Toolbox (CTB) compatible peripheral, any communications software that knows how to work with the CTB can simply access the TelePort directly. Unfortunately, most older communications software was designed to work only with the modem port or printer port, and lacks a setting to talk through the ADB port. CTB-savvy software includes VersaTerm, MacTerminal, PacerTerm, uAccess, QuickMail 2.5, and a couple of shareware offerings, and a CTB-aware update for Microphone II is in the works. Global Village solved this problem for older software by writing special driver software in the form of a system extension that can be set to fool the Mac into watching for software that tries to access either the printer or modem port, and rerouting the communications to the TelePort. The user can decide which of the two serial ports will be "shadowed" by the TelePort. One disadvantage to the way Global Village wrote this software is that the TelePort can be set up either as a CTB device, or with serial port shadowing. It would be much better if it could be set to do either, and block the other method when one was in use. That way the user could use several different communications programs without having to worry about reconfiguring the TelePort software each time. This would not be a terribly difficult thing for Global Village to add; they simply have to add it to their list of things to do.

One of the TelePort's main features is its support of MNP. When the TelePort is talking to another modem that also supports MNP 1 through 4, you should have a reliable connection; no line noise will appear in all but the worst connections. This function, designed by Microcom, has both modems check the data that is being exchanged to be certain that no errors have come through the phone line. If an error is detected, the receiving modem will ask the sending modem to send the garbled information again. In addition, MNP 5 provides data compression, which can increase your "throughput," or the speed at which data travels over the line, as much as two times. This is similar to compressing data using a utility such as StuffIt or Compact Pro, but the compression and decompression are done by the communications device instead of using separate software in the computers at either end, without the user having to do anything special. The disadvantage of this method is that transferring already-compressed files, such as StuffIt archives, can occasionally decrease the speed if you have MNP turned on.

The TelePort actually handles MNP a bit differently from most modems. Rather than implementing the MNP routines in firmware, or in the modem's chips, Global Village chose to handle it within the TelePort software. This would allow for future improvements in the compression technology, and for updates that would not require replacing the modem. Unfortunately, the current software does not handle MNP connections properly all the time, so Global Village is working hard to fix the software and release an update. The recent System 7 compatible release, version 1.06, improves the situation, but doesn't quite eliminate the problem. Users who do experience problems with the MNP function are advised by Global Village's technical support folks to turn off that feature in the TelePort control panel.

[Do note that few, if any, of the online services support MNP. I've recently been dealing with finding UUCP mail servers, many of which use Telebit modems, and several people have said that they don't turn on MNP on those modems because it can cause trouble. Thus, although MNP is excellent if you know you will connect to other modems using MNP, don't assume that everyone uses it. -Adam]