Appendices
47
Appendix D: Glossary
ASCII An acronym for American Standard Code for Information
Exchange. ASCII is a seven-bit code which defines 128 standard
characters, including control characters, letters, numbers, and
symbols. An extra 128 characters comprise the extended ASCII set.
Baud Rate The transmission rate between two serial devices, e.g., modems,
fax machines, etc. Measured in Bits Per Second.
Blind Dialing In blind dialing, the modem continues to dial, regardless of the
existence of a dialtone, ring, or busy signal.
BPS Bits Per Second; the number of bits that can be transmitted in one
second.
Carrier Signal The analog data signal that a modem sends over telephphone wires.
COMx Where (x = 1, 2, 3, or 4), COMx is the name(address) of serial
communications ports on personal computers. Each serial port in a
personal computer has a different number.
CTS Clear To Send.
Default The assumed value that is used for a command parameter when no
other value is explicitly provided.
DCD Data Carrier Detect.
DCE Data Communication Equipment.
DTE Data Terminal Equipment.
DTMF Dual Tone Multi-Frequency (for touchtone dialing).
DTR Data Terminal Ready.
FSK Frequency Shift Keying.
Make/Break Ratio The ratio of the off-hook (make) to on-hook (break) interval is the
make/break ratio in pulse dialing.
Modem A combination of the words MOdulator and DEModulator.
Modems transform digital data into analog signals and back again.
Nonvolatile Memory An area of memory inside the modem where the default
configuration profile is stored. Values recorded in this memory
will not be lost when the power is turned off.
Off-Hook The condition when the modem has picked up the telephone line.
Off-Line Command State
A modem state in which the modem accepts, interprets and
executes commands from an asynchronous computer or terminal.
On-Hook The condition when the modem has not picked up the telephone
line; the telephone is hung up.
On-Line A carrier signal link with a remote modem has been established;
communication is in progress.
On-Line State A modem state in which the modem is connected with a remote
modem. Data can be sent or received from the remote modem in
this state. No commands will be accepted from the modem except
the escape command which will bring the modem into the on-line
command state.
On-Line Command State A modem state in which the modem can accept or execute
commands from an asynchronous computer or terminal while
remaining connected with the remote modem. The user can return
the modem to the on-line state by issuing the AT0n command or
put it into the off-line command state by issuing command such as
ATZ or ATH.
Parity An error-checking method by which the modem verifies that the
data just sent is correct.
Pps Pulse per second.
