Here is a new version of the Express Modem FAQ. The only major changes are
in brief:
1) Unofficial confirmation that there was infact a major bug fix in version
1.1.2 of the Express Modem CDEV. Older versions apparently polled the CPU
unnecessarily even when the modem was inactive (but not turned off).
2) New version of the PowerBook CDEV changes the labeling of the 'internal'
and 'external' modem buttons to 'compatible' and 'normal' respectively.

The Macintosh Express Modem (FAQ) v.1.1

1.1 Introduction

     Ever since the Express Modem (EM) came out there has been a lot of
traffic on the net surrounding the EM. This document is a consolidation of
information that hopefully will answer the most common question that
Express Modem owners, or those considering buy one, might have that are not
well covered elsewhere. It is not intended to replace the manual that comes
with the modem, but it does clarify some issues that are poorly covered in
the manual. It does not attempt to answer any questions you migh have about
the Apple Fax program, or how to make successful connections, but provides
some basic, but essential, information all EM users should be aware of
before they try to tackle more difficult problems. It is mostly directed a
PowerBook users for the simple reason that don’t know enough about its use
on the AV Macs. Most of this is based on personal experience so if you have
any coments, corrections, questions, or hints you want to share don’t
hesitate to contact me.

Espen H. Koht

2 General

2.1 What is the Macintosh Express Modem?

     The Macintosh Express Modem is actually several things.  Unlike most
modems the EM is not just a piece of hardware--it is also the Express Modem
software and this is essential to the operation of the modem. The key to
the EM is that many of the things usually done with special hardware is
done in software by the Macintosh itself. For example, error correction and
compression is done in software rather than hardware.  
     There are currently several different Express Modems. Two of the
modems are intended for use in Powebooks.  One model is for the PB 160 and
180 series, and another for the Duo series. The main difference is the size
of the internal board. There is also an EM for the AV series of desktop
Macintoshes.  Rather than a board that goes into the mac, the AV Express
Modem is mainly the software.  The hardware is the built-in DSP chip in the
AV and an adaptor that attachs to the AV’s GeoPort.

2.2 Can I use the same software with all Express Modems?

     Unlike the hardware the Express Modem software is common to all the
Express Modems. It might work slighly differently depending on what machine
you are using it on, and the AV macs do require some extra bits of
software, but the Express Modem control panel which is the ‘heart and soul’
of the EM is the same as on the Powerbooks. Just make sure you have the
right version of the sofware. ie. both the 880AV and the Duo 230 will work
with version 1.1.2 of the Express Modem software.

2.3 What version of the software do I need to install?

     The most important part of the software package is the Express Modem
panel (CDEV).  This is the heart and soul of the EM--without this your
modem will not work! There have been some (essential!) software revisions
of the Express Modem Control Panel:
1.0     Avoid this! This first version was so buggy that for most people
the modem didn’t work at all with this software! 
1.0.1      Fixed enough bugs to make the modem actually work.
1.0.4      Fixed several more bugs and quirks and improved performance
You should not be using anything older than this version!
1.1.2      New version that works with the AVs (if you have an AV you can’t
use any older versions). According to Apple the only other fix in this
version is improved performance with non-CTB aware programs. This might not
be the whole story. As far as I can tell from informal testing and have had
confirmed by unoffcial sources at Apple, it also fixes a major performance
related bug (see section 2.5 for details).

2.4 Where can I get the latest version of the Express Modem software?

     The latest versions of the Express Modem CDEV available when this
‘goes to print’ is 1.1.2 and it can be found in the Apple Macintosh System
Update, version 2.0.1. This is available directly from Apple and on most
online systems.  

2.5 How much memory does the software take up?

     The Express Modem control panel takes about 81K of system heap and
about 16K of high RAM as an INIT. But that is not all. When the Express
Modem is switched on in the Control Panel an part of it gets loaded as an
invisible bakground application which takes about 450K! (This numbers can
vary). When you turn the Express Modem off, the application quits and frees
up some of the RAM, depending on how fragmented your RAM is.  The big catch
here is that while the EM get turned on automatically the moment the modem
is needed by a program, it will not quit automtically when you are done
with it.  In other words you have to open the control panel and choose
‘off’ you want to reclaim the RAM taken up by the program.  HINT: If you
think this takes too much time you can send a ‘Quit’ appleevent to the
invisible Express Modem application using something like QuicKeys,
AppleScript or Frontier.
NOTE: Your modem will not answer any calls when the modem is off in the
control panel. eg. you will not recieve any faxes.
    If you are running with an older version of the EM CDEV than 1.1.2,
another reason for wanting to turn off the EM is that it takes up quite a
bit of the CPUs time.  When the modem is transfering data the CPU has to do
the work compressing the data and providing error correction. During data
transfers you will probably notice this as a signficant hit if you try
doing something else at the same time.  Unfortunately a bug in the software
used to mean that the EM also grabbed some of the CPUs attention when not
in use! Although this bug has not been officially acknowledged by Apple
unofficial sources at Apple claim that a polling loop that inadvertently
slipped through in previous releases was removed from 1.1.2.

2.6 What is the Express Modem Tool?

     The Express Modem Tool is a Communications Toolbox (CTB) tool that can
be used in programs that use the CTB to make connections.  It is very
similar to the Apple Modem Tool, but has been configured specifically for
the EM to ensure correct setup for most connections.  You don’t have to use
this to use the modem, but it usually makes things simpler. Apparently
there is an incompatibility between version 1.4 of Eudora and this tool,
but you can use the Apple Modem Tool to get around this. So far I haven’t
heard of any other incompatibilities.

2.7 Does the EM have a magic initialization string?

   For some reason you quite often see what I call ‘the magic
initialization string’ for a particular modem posted to the net. This
string is the supposed magic formula that will guarrantie you successful
connections at all times (it almost seems that lenght has some relevance,
as in “Ha! My initialization string is longer than yours!”). Without
denying the the fact that sometimes you need to tweak the modem
configuration to get the desired results, fact is that most of the time you
are probably best off with factory settings. The magic string for the EM is
therefore “AT&F” which restores these settings. 

3 The PowerBooks

3.1 Why did my Express Modem stop working on my PowerBook after I
reinstalled the system?

     To use the Express Modem satisfactorly on a PowerBook you need to have
at least version 7.1.2 of the Powerbook control panel installed. This is
installed when he Express Modem software is intalled from disk. A common
problem occurs when the system on the powerbook is reinstalled after the
Express Modem has been installed, because the system disks usually contain
an older version of the Powerbook control panel which overwrites the newer
one. You should reinstall the PowerBook CDEV from your Express Modem disk
or from Apple’s System Update 2.0.1 after you have reinstalled the system
(the System Update contains version 7.1.3 of the Powerbook CDEV).

3.2 Why does ARA insist that ‘the port is busy’ when I know it is not?

     See section on Internal or Exernal Modem below.

3.3 What should I leave the “Internal or External Modem” radio buttons on
in the Powerbook CDEV?

     In the Powerbook Contol Panel version 7.1.3 or earlier, there is a
section labled “Modem” which has two radio buttons labeled ‘Internal Modem’
and ‘External Modem’. This is probably the poorest documented aspect of the
modem configuration, and the manual even contains some very misleading, if
not directly wrong instructions (eg. p.35). 
In most cases you would want to leave this on ‘External Modem’ (sic.).
Since this is not very intuitive (the EM is an internal modem right?) it is
worth explaining a little further.
     Most macs have two serial ports, and it used to be that if you wanted
to attach modem to your mac it would be connected to either one of them. 
Communication programs only had to know which one of the two to use. 
However, it was soon discovered that this wasn’t always satisfactory. 
First you had the question of what to do when users added more serial ports
to their macs using expansion boards, and then when the internal modems
came out, how to tell the programs to us them and not send thedata out the
serial port.  
To solve this problem (and some others) Apple came up with the
Communcations Toolbox (aka CTB).  The CTB allows any number of ports to be
available, not just the two standard serial ports.  That means that any
program that uses CTB port selection will let you chose whatever ports have
been registered with the CTB.  Thus if you have an internal modem you
should get an ‘Internal Modem’ option in addition to the serial ports in
the CTB port selection phase.
     Most recent commercial communication programs, and quite a few
shareware programs, use CTB port selection, but what about the old software
that doesn’t know about the CTB and assume that just have a standard modem
and printer port?  Well, Apple thought about that and decided to make it
possible to use those too.  In order to do that you have to fool the old
program by taking the information it thinks it is sending to the modem port
and passing it on to the internal modem instead.  This is exactly what you
are telling the computer to do when you make the ‘Internal Modem’ selection
in the Powerbook control panel. Sounds great? Maybe not.  When you do this
there is no way of telling the redirected information from something you
might actually want send out the serial port and not to the modem (eg.
connect to a printer or a localtalk network).  For Duo users this might
prove to be crucial as they only have one serial port on their computer
when undocked. 
     A more appropriate labeling of the buttons should have been something
like ‘Redirect serial port to internal modem: on/off’. 
UPDATE! The newest version of the PowerBook CDEV that comes with the new
Duo’s and the type II batteries apparently has changed the labeling of this
feature. They are now labeled ‘normal’ and  ‘compatible’, representing the
old 'external' and 'internal' buttons respectively. Apart from the labels
there has been no changes in the way these options function, but apparently
the new manual does a better job of explaining things (or at least the
blatant errors have been corrected).

     In most cases you will probably find that your applications understand
CTB port selection, so you should leave the control panel set at ‘External
Modem’. When you do you will find both ‘Internal Modem’ and the usual
serial ports available when you set up your communications program.  If you
have selected ‘Intenal Modem’ you will only see the serial ports, and while
the program will work with your EM with the port set to the modem port, you
will not be able to use the physical modem port for anything.
    One thing to note is that there are quite few programs out there which
are CTB port selection capable without using other features of the CTB. 
For example, just because a program doesn’t let you use the Express Modem
Tool doesn’t mean it doesn’t use CTB port selection!  For example, the
popular shareware program Zterm uses the CTB for port selection and will
work perfectly well with EM in the ‘External Modem’ mode, even though it
doesn’t use the CTB for other things.  The same is true of Appletalk Remote
Access (ARA). If you set the Powerbook control panel to ‘External Modem’
you will be able to choose the ‘Internal Modem’ in the port pop-up in the
Remote Access Setup.  If you do it otherwise you will probably find
yourself stuck with the ‘Remote Only’ option in the Nettwork control panel
on a duo (because you have disabled the printer/localtalk port by
redirecting information from it to the modem) or unable to get ARA running,
all of which is avoidable!
Other common programs that can use CTB port selection are: MicroPhone Pro,
VersaTerm, MacIntercomm, FirstClass Client, MacPPP, InterSLIP etc.