Baud Rate
The number of discrete signal events per second occurring on a communications channel. The
communications carrier frequency. Due to advanced coding methods, each signal can carry
more than one bit. At 300 baud, approximately 300 bits are transmitted per second. For
speeds higher than 2400, baud rate and bit rate are no longer equivalent. Although not
technically accurate, baud rate is commonly used to mean bit rate (bps). In communications
software, baud rate refers to the computer’s serial port rate. See UART.
Bit Rate
The number of binary digits, or bits, transmitted per second (bps). Communications
channels using telephone channel modems are established at set bit rates, commonly 300,
1200, 2400, 4800, 9600, and 14400.
Byte
A group of binary digits stored and operated upon as a unit. A byte may have a coded value
equal to a character in the ASCII code (letters, numbers), or have some other value
meaningful to the computer. In user documentation, the term usually refers to 8-bit units
or characters. 1 kilobyte (K) is equal to 1,024 bytes or characters; 64K indicates 65,536
bytes or characters.
ISDN
Integrated Switched Digital Network- A digital telephone system which provides noise free
high speed communications. The service is a custom service that must be installed by the
phone company. You will need a Terminal Adapter, a telephone provider which supports ISDN,
and a service provider. Usually telephone exchange carriers use digital lines to
communicate with one another, but it is possible to have one of these digital lines
installed directly into your home or office. Results in higher speed, fewer errors, and
allows for separate lines and communications channels. No analog signal is modulated (no
modem), but usually a Terminal Adapter is required because digital signals differ.
Parity
An error-detection method that checks the validity of a transmitted character. Character
checking has been surpassed by more reliable and efficient forms of block-checking,
including Xmodem-type protocols and the ARQ protocol implemented in Courier modems. The
same type of parity must be used by two communicating computers, or both may omit parity.
When parity is used, a parity bit is added to each transmitted character. The bit's value
is 0 or 1, to make the total number of 1's in the character even or odd, depending on
which type of parity is used.
Queue
A waiting line. For example, in a print queue, if a document is sent by person A, then by
person B, then by person C, the jobs to be printed would be stored in a queue, job A would
be printed, then job B, then job C.
UART
Universal Asynchronous Receiver- Transmitter. The controlling component of a serial port.
There are three common types of UARTs: 8250, 16450, and 16550, which are capable of safe
transmission speeds of 19,200 bps, 38,400 bps, and 57,600 bps respectively, though higher
speeds are sometimes possible. Our internal modems have 16550 UARTs built in. External
modems do not have UARTs.
V.32 terbo
Modulation scheme that extends the V.32 connection range: 4800, 7200, 9600, 12K, 14.4K,
16.8K, 19.2K, and 21.6K bps. V.32 terbo modems fall back to the next lower speed when line
quality is impaired, and fall back further as necessary. They fall forward to the next
higher speed when line quality improves.
