Specifications

78 Rockwell Automation Publication AG-SG001G-EN-P - April 2015
Glossary
Digital Data Service (DDS) A special wide-bandwidth Private Leased Line (PLL) that uses digital techniques
to transfer data at higher speeds and with lower error rates than voice-band,
analog PLLs.
DSR Data-Set-Ready. A signal that indicates the modem is connected, powered up,
and ready for data transmission.
DTE Data Terminal Equipment. Equipment that is attached to a network to send or
receive data, or both. Programmable controllers, workstations, and interface
modules are examples of DTEs.
DTR Data-Terminal-Ready. A signal that indicates the transmission device (terminal)
is connected, powered up, and ready to transmit.
EOT End Of Transmission. An ASCII control character that indicates the end of a
data transmission.
FCC Federal Communication Commission (United States).
Full-duplex Circuit A physical circuit that allows simultaneous, bidirectional transmission of data;
also called a ‘four-wire’ circuit.
Full-duplex Modem A modem that is capable of simultaneous, bidirectional transmissions.
Full-duplex Protocol 1) A mode of operation for a point-to-point link with two physical circuits, in
which messages or transmission blocks can be sent in both directions at the same
time.
2) Contrasted with two-way alternate.
General Switched
Telephone Network
International version of a public-switched telephone network.
Half-duplex Circuit A physical circuit that allows transmission of data in either direction but not at
the same time.
Half-duplex Modem A modem that sends and receives messages on carriers of the same frequency.
Therefore, simultaneous, bidirectional transmissions are not possible.
Half-duplex Protocol 1) A mode of operation for a point-to-point or multipoint baseband link with
two physical circuits, in which messages or transmission blocks can be sent in one
direction or the other but not both at the same time.
2) Contrasted with two-way simultaneous. The master station-to-remote station
communication uses a half-duplex protocol.
Handshake A series of signals between a computer (DTE) and a peripheral device (DCE; for
example, a modem) that establishes the parameters required for passing data.