USR fought back with a 16,800 bit/s version of HST, while AT&T introduced a one-off 19,200 bit/s method they referred to as V.32ter, but neither non-standard modem sold well. In the early 90s, V.32 modems operating at 9600 bit/s were introduced, but were expensive and were only starting to enter the market when V.32bis was standardized as well. The introduction of these higher-speed systems also led to the development of the digital fax machine during the 1980s.

These values are maximum values, and actual values may be slower under certain conditions . For a complete list see the companion article list of device bandwidths.

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"Voice" and "fax" are terms added to describe any dial modem that is capable of recording/playing audio or transmitting/receiving faxes. Early modems – both acoustically coupled and directly connected – could not place or receive calls on their own, but required human intervention for these steps. As telephone-based 56k modems began losing popularity, some Internet service providers such as Netzero/Juno, Netscape, and others started using pre-compression to increase apparent throughput. This server-side compression can operate much more efficiently than the on-the-fly compression performed within modems, because the compression techniques are content-specific (JPEG, text, EXE, etc.). Website text, images, and Flash media are typically compacted to approximately 4%, 12%, and 30%, respectively. The drawback is a loss in quality, as they use lossy compression which causes images to become pixelated and smeared. ISPs employing this approach often advertise it as "accelerated dial-up".

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As described above, technologies like Wi-Fi and Bluetooth also use modems to communicate over radio at short distances. The CDMA versions do not typically use R-UIM cards, but use Electronic Serial Number instead. Different terms are used for broadband modems, because they are frequently contain more than just a modulation/demodulation component. Other broadband modems include satellite modems and Expat Shield power line modems.

By the time technology companies began to investigate speeds above 33.6kbit/s, telephone companies had switched almost entirely to all-digital networks. As soon as a phone line reached a local central office, a line card converted the analog signal from the subscriber to a digital one, and vice versa. The ITU standard V.34 represents the culmination of these joint efforts.

A dialup modem will not function across this type of line, because it does not provide the power, dialtone and switching that those modems require. A leased line modem also uses ordinary phone wiring, like dial-up and DSL, but does not use the same network topology. Voice modems are used for computer telephony integration applications as simple as placing/receiving calls directly through a computer with a headset, and as complex as fully automated robocalling systems.

A baud is one symbol per second; each symbol may encode one or more data bits. 48 kbit/s upstream rate would reduce the downstream as low as 40 kbit/s due to echo effects on the line. To avoid this problem, V.92 modems offer the option to turn off the digital upstream and instead use a plain 33.6 kbit/s analog connection in order to maintain a high digital downstream of 50 kbit/s or higher. The first 56k dial-up option was a proprietary design from USRobotics, which they called "X2," because 56k was twice the speed of 28k modems. Modem manufacturers discovered that, while the analog to digital conversion could not preserve higher speeds, digital to analog conversions could. While that signal still had to be converted back to analog at the subscriber end, that conversion would not distort the signal in the same way that the opposite direction did.

It employs the most powerful coding techniques available at the time, including channel encoding and shape encoding. This rate is near the theoretical Shannon limit of a phone line. Consumer interest in these proprietary improvements waned during the lengthy introduction of the 28,800 bit/s V.34 standard. While waiting, several companies decided to release hardware and introduced modems they referred to as V.FAST. V.32bis was so successful that the older high-speed standards had little to recommend them.

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