28.8/33.6/56 kbps Modems

28.8 or 33.6 kbps (V.34) modems, under ideal phone line conditions, will transmit and receive data at 28,800 or 33,600 bits per second, and 56K (X2, K56, or V.90 modems) will typically transmit data at up to 33.6 kbps, and receive data at up to about 50,000 kbps (more or less). Because all of these modems can use data compression, they can achieve throughputs of 2 or more times those rates on compressible files.

The original V.34 standard, which was finalized in the spring of 1995, included speeds up to 28.8 kbps. An improved version of the V.34 standard was finalized in the fall of 1996 which added the speeds of 31.2 Kbps and 33.6 Kbps. The speeds are optional, enabled at a manufacturer's discretion and negotiated at the beginning of a call. AT&T Paradyne, Penril, Zypcom and Motorola were among the first selling 33.6 modems, but those were mostly high-end modems. USR got the jump on most other manufacturers of consumer-grade modems by adding 33.6 capability to their V.34 Courier and part of their Sportster lines. Soon most other consumer-grade modem manufacturers released 33.6 models. For many people that already had 28.8 modems, there was little reason to spend money replacing a 28.8 modem with a 33.6 -- most of them upgraded directly to a modem that supported the V.90 56 kbps standard when it was finalized. Whatever speed modem you have, note that your service provider must support it at their end. That is, even if you have a 56K modem, you won't be able to get a connection above 33.6 kbps unless your Internet Service Provider (ISP) and the other places you normally call also have 56 kbps modems (these days most do). Also, many phone connections simply will not support speeds that high -- so if you have a 33.6 modem now and can't get 33.6 or 28.8 connects, it is doubtful that you would get substancial improvement by buying a 56K modem (so borrow one first and try it out). More on this topic later.

As mentioned above, the current 28.8/33.6 modem standard is V.34. However, before the V.34 standard was finalized there was another 28.8 protocol called V.FC. V.FC was an interim protocol developed by Rockwell and introduced ahead of the V.34 standard in a effort to capture market share. While many modems still support V.FC, the V.34 protocol is more robust and before the advent of 56K modems, the industry had pretty much universally switched over to V.34 as their main protocol. If you are buying a used 28.8 modem, be careful you don't buy one that only supports V.FC or you may find you cannot connect to many ISPs and BBSs. If you buy a V.34 modem, you may want to also make sure it supports V.FC if you communicate with a variety of other modems on older systems (a number of manufacturers do not include V.FC support in their V.34 modems). Note that the V.34 and V.90 standards are in some ways like a tool-box: there are many optional parts, and manufacturers can pick and choose which of the options they want to include. Cheaper modems generally implement fewer of the options, which may limit throughput or flexibility. For example, many low-end modems do not support split (asymmetrical) transmit/ receive speeds, which often substantially reduces their performance.

Regarding support and upgrades: The V.34 and the V.90 standards are now mature and the new modem products which use them are fairly stable, meaning the amount of support needed from the manufacturer is generally less than it was when the standard was new. So having a V.34 or V.90 modem with flash ROM (which allows upgrading of the modem's firmware by downloading an update electronically) is not as critical as it was when the standards were inmature (but it is still a desirable feature in a hardware modem). And now that "Software Modems" are in wide use, new software drivers are frequently needed when you upgrade your operating system (for example to Windows XP). Most reputable modem manufacturers have on-line support on their web site. But if you get a cheap, no-name modem, your chances of getting any future upgrades or any other type of support will probably be slim to none.