Envoy ACP/XF Configuration and Management Manual

Glossary
EnvoyACP/XF Configuration and Management Manual—429232-003
Glossary-2
CTS
CTS. Clear to send. A signal that comes from a modem, indicating to the computer
equipment that the modem is ready to accept data for transmission.
DCE. Data circuit-terminating equipment. DCE generally refers to the modem to which a
terminal or host computer (called the DTE) is connected.
DSC. Dynamic System Configuration. This is an online configuration program introduced in
the C-series Guardian 90 operating system. It allows the user to add peripherals to a
running system. COUP is the user interface to DSC.
DSR. Data set ready. A signal coming from a modem, which usually indicates to the
computer equipment that the modem is powered on.
DTE. Data-terminal equipment. DTE is the terminal or host computer to which a modem
(called the DCE) is connected.
EBCDIC. Extended binary-coded decimal interchange code. A method of coding data
designed for synchronous use. It consists of 8 bits of data with no parity bit. There are
256 standard characters.
FCS. Frame-checking sequence. The field in a bit-synchronous frame that contains the
cyclical redundancy check (CRC) value for the frame, used to verify correct data. It is a
16-bit field, immediately preceding the ending flag for the frame.
flag. A unique field found at the beginning and end of bit-synchronous frames, used for
frame synchronization and transparency control. Always set to the hexadecimal value
7E (01111110).
frame. The basic transmission unit within a bit-synchronous communications environment.
Frames are made up of the following fields: beginning flag, address field, control field,
information field, and frame-check sequence and closing flag.
full-duplex. A method of serial communications in which the data flow between two points
can occur in both directions simultaneously. This concept refers to the physical
capability of the line.
half-duplex. A method of serial communications in which the data flow between two points
can occur in only one direction at a time. This concept refers to the physical capability
of the line.
HDLC. High-level Data Link Control. A bit-synchronized data communications protocol.
Uses ABM communications between stations. See also ABM.
information field. The field in a bit-synchronous frame that contains data or additional
control information. If present, the information field follows the control field and varies
in length.
I-frame. See information frame.