Synchronous V.34 Modems

Is my modem H.324 compatible?

To do standards-based videoconferencing over the PSTN ("POTS") using H.324, you must have an "H.324 compatible," or synchronous V.34 modem, such as those listed below. There are two types on the market, V.80 and Rockwell Video Mode (a.k.a. RVM and VRPI), although V.80 is by far the most prevalent. To determine whether you have one of these modems, use a program that allows you to enter AT commands to the modem directly, e.g., Terminal, HyperTerm, Procomm, or QuickLink III. Some modems support V.80 and VRPI. A V.80 modem will respond with "OK" to the following AT command:

and a VRPI modem will respond with "OK" to this command:

Note that some H.324 products will only work with V.80 modems and not VRPI modems. Smith Micro's VideoLink 324 and AudioVision products work with both. Also note that "V.80" and "VRPI" refer to the interface between the modem and the software--the DTE interface--and not between modems--the DCE interface. IOW, if you have a V.80 modem and your friend has a VRPI modem, you can still talk to each other because they produce the same bit stream.

Can I still somehow use my non-H.324-compatible modem for videoconferencing?

Yes, some products, such as VideoLink and AudioVision allow you to use just about any modem, even ancient 14.4kbps V.32bis and good-old V.34 modems, but both ends of the connection must use software from the same vendor. This is because there is no standard for this. As a matter of fact, I call this NCOM mode, "Non-Compliant Old-Modem mode." :-) I have noticed that some products from different vendors happen to be compatible with each other using this mode, but this is nothing on which you the consumer should depend.

What modems are H.324 compatible?

DISCLAIMER: This list is not complete--I will continue to add to it as I learn of other synchronous V.34 modems--but to the best of my knowledge, it is accurate. However, manufacturers can change the specs on modems at any time, so there is no guarantee that if you buy one of these modems that it will indeed by "H.324 compatible" or work with a specific H.324 terminal.

3Com Corp., U.S. Robotics 56K Voice Faxmodem with Speakerphone (I have heard reports that some versions of the firmware do not in fact support V.80) and 33.6 Voice/Video Faxmodem (only available with Bigpicture) (both V.80). U.S. Robotics technical support told me and others that Courier V.Everything supported V.80, but I'm beginning to believe that they are mistaken.

ActionTec Electronic, Inc., MobileLinkTM Voice/Data/Fax/Modem (V.80).

Best Data Products, Inc., Smart One 336F, 336VF, 336VLX, 336SP/SPX, 56F, 56VF, 56VLX, and 56SP/SPX (V.80).

Boca Research, Inc., 56K Internet Modem, 33.6 Speakerphone External, and 56K Home Office Modem (V.80)

Diamond Multimedia Systems, Inc., SupraFAXModem and all 33.6kbps and 56kbps modems, including SupraSonic and SupraExpress models (V.80)

Digicom Systems Inc., Modem Blaster Flash 56 (V.80)

ELSA, 56K (V.80)

IBM Corporation, IBM 56K PC Card Modem/Cellular Capable (V.80)

Logicode Technology, 56,000bps Internal Data/Fax Modem (V.80)

Motorola, Inc., VoiceSURFR/ModemSURFR 56K (V.80)

Phoebe Micro, Inc., Phoebe 56K internal modem CMV1456VQH-Plus (V.80 and RVM)

Pretec, MODEM 56 PC CARD and 56K CompactModem Card (V.80) I have heard reports that the PC Card modem does not truly support V.80.

Conexant (was Rockwell International), K56flex™ 56Kbps Modems with optional SVD (Simultaneous Voice and Data) (V.80 and Rockwell video ready synchronous access mode); 336 ACi/ACF Modem Product Line (Rockwell's synchronous access mode: Rockwell Video Mode (RVM))

Shark Multimedia, Inc., Leopard 56K and Leopard FM 56K (V.80)

Zoom Telephonics Inc., "As of January 1998 all Zoom shipments of V.34 or 56K internal or external North American modems include V.80. Zoom's international products are scheduled to support V.80 with an easy software download no later than the second quarter of 1998." (V.80)