Rockwell Automation DAG6.5.8 APPLICATION GUIDE SCADA SYSTEM - Manual (Page 408)

Publication AG-UM008C-EN-P - February 2005
4 Glossary
Packet Radio Modem An intelligent radio modem that packetizes the data it receives
from the transmitting station. The modem places a header and a
trailer around the data before it transmits the data to the
destination device. The header can also contain routing
information. Packet radio modems also perform their own data
error checking and will re-transmit the data if an error is
encountered.
PAD Packet assembler/disassembler. Equipment used to assemble and
disassemble data packets for transmission on a packet-switching
network such as a satellite system.
Parallel port An electrical connection on a computer capable of transmitting or
receiving two or more bits of data at one time; the
communications port to which such devices as parallel printers
can be attached.
Point-to-multipoint A network where connections exist between one master station
and multiple remote stations.
Point-to-point A network where a connection is made between two and only
two terminal installations.
Poll When the master station sends a message to a remote station that
allows the remote station an opportunity to return a response to
the master or another remote station. In this manual, when the
master polls a remote station, it is not initiating a read request.
Polling cycle The order and frequency in which network nodes in a poll list
are polled.
Poll List A list of nodes or stations on a network to be polled on a regular
and repeated basis.
Protocol A set of conventions governing the format and timing of data
transmission between communication devices, including
handshaking, error detection, and error recovery.
Private Leased Line
Network (PLL)
A dedicated voice-band telephone line between two or more
locations primarily used for data transmission.
Public Switched Telephone
Network (PSTN)
The standard dial-up telephone network originally used for
voice communication.
RS-232 An EIA electrical connection standard, most often used as a
standard interface for serial binary communication between data
terminal equipment and data communications equipment. Also
known as EIA–232.
RTS Request To Send. A request from the module to the modem to
prepare to transmit. It typically turns on the data carrier.
RTU Remote Terminal Unit. See remote station.