Nonvolatile Memory (NVRAM)
User-programmable random access memory whose data is retained when power is turned off. On the USRobotics modem, it includes four stored phone numbers and the modem settings.

Off/On Hook
Modem operations that are the equivalent of manually lifting a phone receiver (taking it off-hook) and replacing it (going on-hook).

Online Fall Back/Fall Forward
A feature that allows high-speed, error-control modems to monitor line quality and fall back to the next lower speed in a defined range if line quality diminishes. As line conditions improve, the modems switch up to the next higher speed.

Originate Mode
The mode used by your modem when initiating an outgoing call to a destination modem. The transmit/receive frequencies are the reverse of the called modem, which is in answer mode.

Parity
A simple error-detection method that checks the validity of a transmitted character. Character checking has been surpassed by more reliable and efficient forms of error checking, including V.42 and MNP 2-4 protocols. Either the same type of parity must be used by two communicating computers, or both may omit parity.

Point-to-Point Protocol (PPP)
A protocol used to send data over serial lines. PPP provides error checking, link control, and authentication, and can be used to carry IP, IPX, and other protocols. PPP is superseding SLIP as the leading dial-in protocol.

Protocol
A system of rules and procedures governing communications between two or more devices. Protocols vary, but communicating devices must follow the same protocol in order to exchange data. The format of the data, readiness to receive or send, error detection and error correction are some of the operations that may be defined in protocols.

RAM
Random Access Memory. Memory that is available for use when the modem is turned on, but that clears of all information when the power is turned off. The modem's RAM holds the current operational settings, a flow control buffer, and a command buffer.

Rate Adaption
This allows for the transfer of synchronous or asynchronous data.

Remote Digital Loopback
A test that checks the phone link and a remote modem's transmitter and receiver.

Remote Echo
A copy of the data received by the remote system, returned to the sending system, and displayed on the screen. Remote echoing is a function of the remote system.

ROM
Read Only Memory. Permanent memory, not user-programmable.

Serial Transmission
The consecutive flow of data in a single channel. Compare to parallel transmissions where data flows simultaneously in multiple channels.

Start/Stop Bits
The signaling bits attached to a character before and after the character is transmitted during asynchronous transmission.

Terminal
A device whose keyboard and display are used for sending and receiving data over a communications link. Differs from a microcomputer or a mainframe in that it has little or no internal processing capabilities.

Terminal Mode
Software mode that allows direct communication with the modem. Also known as command mode.

Throughput
The amount of actual user data transmitted per second without the overhead of protocol information such as start/stop bits or frame headers and trailers. Compare with characters per second.

TurboPPP
TurboPPP is USRobotics unique combination of asynchronous-to-synchronous PPP conversion, compression, multilink PPP (ML-PPP). You can use TurboPPP to access the Internet or remote local-area networks (LANs) at speeds of up to 128 kbps before compression and up to 512kbps with compression.

USB (Universal Serial Bus)
USB transfers isochronous or asynchronous data and is used to replace the cable "clutter". USB is designed as "plug and play." This means devices such as modems are automatically detected once they are attached to your computer.

V.8
The ITU-T standard specification that covers the initial handshaking process.

V.110
V.110 is a fixed-frame rate adaption that subdivides the ISDN channel into a single speed data channel.

V.120
V.120 allows one B-channel to carry multiple subrate channels in a succession of statistically multiplexed frames.

V.17 Fax
An ITU-T standard for making facsimile connections at 14,400 bps, 12,000 bps, 9,600 bps, and 7,200 bps.

V.21
An ITU-T standard for modems operating in asynchronous mode at speeds up to 300 bps, full-duplex, on public switched telephone networks.

V.22
An ITU-T standard for modem communications at 1,200 bps, compatible with the Bell 212A standard observed in the U.S. and Canada.

V.22 bis
An ITU-T standard for modem communications at 2,400 bps. The standard includes an automatic link negotiation fallback to 1,200 bps and compatibility with Bell 212A/V.22 modems.

V.27 ter
An ITU-T standard for facsimile operations that specifies modulation at 4,800 bps, with fallback to 2,400 bps.

V.29
An ITU-T standard for facsimile operations that specifies modulation at 9,600 bps, with fallback to 7,200 bps.

V.32
An ITU-T standard for modem communications at 9,600 bps and 4,800 bps. V.32 modems fall back to 4,800 bps when line quality is impaired.

V.32 bis
An ITU-T standard that extends the V.32 connection range: 4,800, 7,200, 9,600, 12,000, and 14,400 bps. V.32 bis modems fall back to the next lower speed when line quality is impaired, fall back further as necessary, and also fall forward (switch backup) when line conditions improve (see online fall back/fall forward).

V.34
An ITU-T standard that currently allows data rates as high as 28,800 bps.

V.34+
An enhancement to V.34 that enables data transfer rates as high as 33,600 bps.

V.42
An ITU-T standard for modem communications that defines a two-stage process of detection and negotiation for LAPM error control.

V.44
An ITU-T standard for modem data compression. It provides for a 6:1 compression ratio.

V.90
The ITU-T standard for 56 Kbps modem communications. This technology uses the digital telephone network to increase the bit rate of the receive channel by eliminating the analog to digital conversion commonly found in modem connections. V.90 connections require a modem with V.90 or x2 technology calling a digitally connected Internet Service Provider or corporate host site compatible with V.90 or x2 technology.

V.92
The ITU-T standard for advanced 56 Kbps modem communications. This technology offers three new features to enhance the V.90 standard. The first feature is V.PCM-Upstream, which allows a modem’s upstream communication to reach speeds of 48,000 bps. The second feature provides quicker connection times by allowing the modem to remember the line conditions of a V.92 supported service provider. The third feature is the Modem on Hold technology, which allows your Internet connection to be suspended when there is an inbound telephone call, then return to the connection when the call is completed without losing the connection. The V.92 technology can only be utilized if a V.92 modem is dialing into an Internet Service Provider that supports and provides a digital V.92 signal.

World Wide Web (WWW)
A part of the Internet designed to allow easier navigation of the network through the use of graphical user interfaces and hypertext links between different addresses.

X.75
X.75 defines the connection between public networks such as larger computers and mainframes.

Xon/Xoff
Standard ASCII control characters used to tell an intelligent device to stop/resume transmitting data.

Contents:

Appendixes

Courier 56K Corporate Modem Command Reference

Glossary of Terms