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Issue 2 - 07/00 A4-9
Appendix 4—Glossary & Abbreviations
Parity
A mechanism for determining whether a single bit error
has occurred when individual characters are being
transmitted. Parity is transmitted as an additional bit in
the character frame, and may take the values
None
,
Odd
or
Even
.
None
means that a parity bit is not included—
i.e. there is no error detection.
Odd
means that either a
zero or a one is transmitted, such that the total number of
bits sent in a character, including the parity bit, is odd.
Even
works in the same way, but ensures that the total
number of transmitted bits is even.
PC
Personal Computer.
PCM
Pulse Code Modulation.
Physical Layer
The lowest layer of the OSI model, which is responsible
for the electrical, mechanical and interface aspects of
transmitted data. Also known as Layer 1.
PMP
Point to Multipoint.
Point to
In Point to Multipoint mode up to 8 terminals can be
Multipoint
connected in parallel along the bus. The length of the bus
is limited to about 200m, depending on the cable.
Point to Point
In Point to Point mode one Terminal Equipment (TE) is
connected at the end of up to 1km of cable.
Port
The physical access point into and out of an electrical
equipment or network.
PP
Point to Point.
PRI
Primary Rate ISDN.
Protocol
A set of rules, usually defined by a standards making body,
for carrying out a specific function such as exchange of
information between systems, synchronisation, error
checking, etc. Examples of protocols are ETSI and 1TR6.
PSPDN
Packet Switched Public Data Network.