This is a traditional controller based modem from a manufacturer with a solid product history. The modem includes its own control processor which understands AT commands directly, so only a basic USB serial driver is needed. This modem was recommended in a Macintouch user report and is often available from Amazon or eBay for under $25 (used).
Recommended for USA
Users report this modem does not recognize Caller ID in the UK even though it includes a UK landline connector and works for dial-up networking.
Testing Notes: In my testing this modem worked well. No software installation was necessary. When I plugged the modem in, I was alerted that a new device had appeared. In the Network Preferences panel, I selected USB Modem -> Advanced -> Modem -> Vendor: Zoom, Model: Universal (115K). I also tested faxing with this modem and it worked without incident.
This modem may fail to be found on Mac OS X El Capitan because its driver did not load. If so, you can try temporarily disabling the System Integrity Protection feature as described here. In my testing this allowed the standard modem driver to load. While I expect Apple will fix this problem eventually, it may not be seen as a high priority. Alternatively, you can use the USR modem below which comes with its own low level driver.
This is a traditional controller based modem from a manufacturer with a solid product history. The modem includes its own control processor which understands AT commands directly, so only a basic USB serial driver is needed. The USR5637 is available from Amazon for around US$50.
Recommended for international users
Users report this modem does recognize Caller ID in the UK, but does not come supplied with a UK compatible landline cable, so you may need an appropriate adaptor cable.
Testing Notes: In my testing, this modem worked well. The manual included with the modem is unclear about the installation procedure. You'll need to install the software from the included CD first, and then plug-in the modem for it to be recognized by Mac OS X. In the Network Preferences panel, select USB Modem, click Advanced, set the Vendor to "Other", and Model to "USRobotics 56K USB Modem". I also tested faxing with this modem and it worked without incident.
This modem is about the size of a cell phone (significantly larger than the Zoom or Apple USB Modem). There is no speaker, so to hear the modem dial and connect you must pickup a handset. A USR5637 online User Guide is available.
I had no trouble running both the Apple USB Modem and USRobotics Modem at the same time. Having run both modems continuously over an extended period, I prefer the USRobotics modem for its stability. It's more modem for about the same price.
[16-Jun-2011 - The Apple USB Modem is no longer supported on newer Macs running Mac OS X Lion because the modem driver is a 32-bit kernel extension and Lion boots with a 64-bit kernel by default. MacBooks and older 32-bit CPUs (prior to the Core 2 Duo) still run a 32-bit kernel.]
This is a controllerless or software modem based on the Motorola SM56 design. The advantages of a software modem are low cost, low power consumption, and compact design. The disadvantage is that modem processing is offloaded to a specialized driver that runs on the host computer. In this case, Apple has customized Motorola's driver to produce a generally solid product. At the time of this writing, Apple has discontinued the Apple USB Modem (MA034Z/A) but they are still available from Amazon for around US$50.
No longer recommended
Testing Notes: Software modems require a driver that can pump real-time audio like data to the modem's transceiver regardless of any other system software that may be running. In my own testing, I've found it's important to connect the modem to a reliable USB Hub as close to the host computer as possible. Apple's USB Modem driver generally worked well but could fail under certain conditions like launching Disk Utility with external FireWire drives attached. I tend to prefer controller based modems for their greater stability, but many people already have an Apple USB Modem.
If Phone Amego has trouble opening a connection to your modem, quit Phone Amego, unplug and then replug the modem to reset the driver, and then relaunch Phone Amego.
I've had one problem report where the Apple USB Modem failed to decode the caller ID signal as expected. Searching on-line indicates the problem is rare and may be related to the quality of the phone line.
Some Apple Internal Modems support CallerID but this is not universal. Since new Macs no longer come with built-in modems, I was unable to test this feature.
Some users report this generic unlabeled modem worked well for them. Conexant designs and sells modems to other manufacturers to bundle with their systems. I haven't tried this modem myself, but I understand Conexant is a leading supplier of voice modems. If you can find a reliable source for one of these, it certainly is a good price.
Here is the report from the Apple USB Profiler:
Product ID: 0x1329
Vendor ID: 0x0572 (Conexant Systems, Inc.)
Serial Number: 24680246
Speed: Up to 12 Mb/sec
If you don't mind some risk, this generic modem could be enough. Conexant doesn't sell directly to end users or in quantities less than 1000, so an importer with access to their production could do very well. The trade-off is that you don't know which model you are actually getting until it arrives, and there is no warranty, or after sale support.
15-Feb-2013: One user reports receiving an "Agere SoftModem" which is not compatible with Mac OS X despite the Conexant label on the package.
Which Do I Prefer?
The Zoom is more compact, doesn't need you to install a driver, and is often available used at a lower price. Both have worked well for me. Online reports indicate the Zoom does not work in the UK. The USR is more compatible for international use, but for domestic Mac users, the Zoom is a nicer package. If your phone line is marginal or you've had trouble with other modems, I would try the USR.
If you order from Amazon using one of the links on this page, I get a small referral credit. Thank you.
In my own testing, Mac OS X could sometimes fail to open a connection to the modem device, and it was necessary to unplug and then re-plug the USB hub the modem was attached to in order to reset the connection (hot plugging just the modem itself was not sufficient). After replacing three smaller hubs with a single 7-port hub, the problem has not reoccured. If your USB modem is chained off your Monitor or Keyboard and you experience some instability, try attaching it directly to your computer, or through a single hub connected directly to your computer.
The Cables-to-Go hub (or clone) linked above has worked well for me. Its best feature is that each port works at the maximum possible speed and supplies full power regardless of what else is connected (when the included power adaptor is used).
If you have trouble getting Phone Amego to startup, press and hold the Command key while launching to turn monitoring off. You can then enable each device one at a time to see if one is not responding.