Wyse 3315SE, Справочное руководство, Страница: 249 / 260

Glossary 225
Null modem A cable, especially an RS-232 cable, for connecting serial ports
on two computers directly, rather than via modems. Since,
according to the specification, both computers should transmit
on pin three of their RS-232 connectors and receive on pin two,
a null modem cable needs to connect one computer's pin two to
the other's pin three and vice versa. It also needs to have male
connectors at both ends (again, according to the specification).
OSD On Screen Display.
Packet A group of bits (including data and call control signals)
transmitted as an identifiable unit on a packet-switched network
(PSN).
PAP Password Authentication Protocol. An authentication scheme
used by PPP servers to validate the identity of the originator of
the connection. PAP applies a two-way handshaking procedure.
After the link is established the originator sends an id-password
pair to the server. If authentication succeeds the server sends
back an acknowledgment; otherwise it either terminates the
connection or gives the originator another chance.
Parallel port An input/output port that allows the entire bit pattern for a single
character to be sent at one time, usually used to connect a
printer to a computer.
Parity check The addition of non-information bits (specifically, parity bits) to
make up a transmission block (a number of bits transmitted as
unit) that ensures the total number of ones is always either even
(even parity) or odd (odd parity). The parity check is used to
detect transmission errors.
PCMCIA Personal Computer Miniature Connector Interface Adapter.
Hardware and software standards for credit-card-sized
integrated circuit cards.
Ping Packet InterNet Groper. A protocol used in the Transmission
Control Protocol (TCP) environment to test whether a node or
remote device is communicating on a local area network (LAN)
or wide area network (WAN). The protocol provides for
transporting an echo response from a host system, a client, or a
gateway. It is a useful tool for locating problems on the network
related to failed connections and software problems. One
datagram is sent every second over the network and any
response is displayed.