Specifications

Engineering Guidelines
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NAT – Network Address Translation. A means of translating internal IP addresses to a defined
limited range of internet IP addresses. The benefit is the ability to use a limited range of internet
addresses and map these to a much larger internal range.
NIC – Network Interface Card. Physical connection to the network. In a PC, this is often a
plug-in card.
NSU – Network Services Unit. This interface connects between the PSTN Primary Rate trunks
and the ICP.
ONS – On-Premise Line. This is a two-wire analog telephony interface, within an office
environment, and not passed outside.
OPS – Off-Premise Line. This is a two-wire analog telephony interface, typically installed
external to a building, e.g. external shed or guard house.
OSPF – Open Shortest Path First. A link-state routing protocol used for routing IP traffic over
the most cost-efficient route.
PC – Personal Computer.
PCM – Pulse Code Modulation. The digital representation of analog signals.
PDA – Personal Digital Assistant. A handheld personal organizer that can interface to a PC
or a Mitel PDA Phone.
Permanent IP – An IP address that has been leased (from DHCP) on a permanent basis.
PI – Performance Index. A calculation of the performance limits of a system. Different weighting
values are assigned to various types of calls. Based on the expected calls per hour (CPH) of
all of the user ports on the system, a system performance index (PI) can be calculated. The
system PI is used as an indication of how much traffic the 3300 ICP can handle at any one time.
Ping – This is a means of sending a test message and waiting for a reply to determine if a
network device is reachable. On a PC, this is invoked with the command ping.
PPM – Parts Per Million. This is a measurement of accuracy, or the expected error in one
million events. Therefore 1 ppm means that 999,999 to 1,000,0001 events occurred when
1,000,000 were expected. This is 0.0001% error. For example, a household clock that is 1
second accurate per day is 11.5 ppm, or would need to be 0.086 seconds incorrect per day to
be 1 ppm.
PRI – Primary Rate Interface. This is a connection to the PSTN where a number of trunk
channels are multiplexed onto a common connection. Both T1 and E1 variants are available.
PSTN – Public Switched Telephone Network. The telephone network that provides local and
long distance connections, e.g. Bell, AT&T, BT.
PTT – Poste, Telefonie, Telegrafie. PSTN services. Often countries combine postal services
and telephony under a common service provider, e.g. the government.