3Com 3C10402B Administrator's Manual page 560

560 G
LOSSARY
Layer 1 Physical layer
out-of-band signaling An extra signal transmitted with the information signal to monitor and
control a transmission. It provides an additional layer of resilience by using
a separate channel.
P
packet A collection of bits, including address, data, and control information, that
are transmitted together. The terms frame and packet are often used
synonymously.
packet buffer Memory space reserved for storing a packet awaiting transmission or for
storing a received packet.
packet switching A method of switching data in a network. Individual packets of a set size
and format are accepted by the network and delivered to their
destination. The sequence of packets is maintained, and destination
established, by the exchange of control information (also contained in the
packets) between the sending terminal and the network before the
transmission starts.
paging 1) A communications service that includes a one-way beeper service,
one-way text service, and two-way text and voice service.
2) A public address announcement system. Many PBX telephone systems
can do paging through the speakers in the telephone sets.
PBX Private Branch eXchange. An in-house telephone switching system that
interconnects telephone extensions to each other, as well as to the
outside telephone network. It can include functions such as least cost
routing for outside calls, call forwarding, conference calling, and call
accounting.
PCS Personal Communications Services. Refers to a variety of wireless services
emerging after the U.S. Government auctioned commercial licenses in
late 1994 and early 1995.
phantom mailbox A user profile that uses a telephone number with no associated
telephone. Messages can be sent to the phantom mailbox from within
the voice mail system. The Auto Attendant can route messages to the
phantom mailbox, and you can dial the phantom mailbox directly.