TB9400/TN9275 Installation and Operation 151
© Tait International Limited May 2023
multicast IP 
address
An IP address that refers to a group of hosts rather than a single host. These 
hosts will all accept packets with this IP address.
NAC Network Access Code. The 12 most significant bits of the network 
identifier information that precedes every packet sent on the CAI. The 
NAC identifies which network the data belongs to, allowing base stations 
and mobiles to ignore packets belonging to interfering networks.
NAT Network Address Translation allows the use of a single IP address for a 
whole network of computers. A NAT sits between the public Internet and 
the network it serves, and works by rewriting IP addresses and port 
numbers in IP headers on the fly so the packets all appear to be coming 
from (or going to) the single public IP address of the NAT device instead 
of the actual source or destination.
network element Any device that is network-connected. A Tait digital network consists of a 
number of network elements. The TB9400 base station is a network 
element designed and manufactured by Tait.
NTP Network Time Protocol is a protocol and software implementation for 
synchronizing the clocks of computer systems across a network. An NTP 
server obtains the correct time from a time source and sets the local time in 
each connected computer.
Offline mode A mode of operation in which active service is suspended so that special 
operations can be carried out, such as programming in a new configuration 
or carrying out invasive diagnostic tests.
Online mode The normal operating mode of the base station.
over A single transmission, which begins when a user presses PTT and ends 
when the user stops pressing.
PA The Power Amplifier is a base station module that boosts the exciter output 
to the required transmit level.
PMU The Power Management Unit is a module in the base station that provides 
power to the subrack and monitors power conditions. 
PTT Push To Talk. The button on an SU that keys the transmitter.
QoS Quality Of Service. A router feature that gives real-time data such as voice 
calls priority over other data.