2 Terms
2.0.1 Public address（PA）
Sound broadcast managed by using organization to serve the public within the area occupied by the user，including business announcement，background broadcast and emergency broadcast.
2.0.2 Public address system（PAS）
The system composed of all the PA equipment，facilities and acoustic environment of the PA coverage area.
2.0.3 Public address equipment（PAE）
General term for all equipment in the PAS，including loudspeakers，power amplifiers，transmission lines，transmission equipment，management（or control）equipment，paging equipment，microphone and other signal source equipment.
2.0.4 Emergency broadcast
Broadcast released by the PAS to its service zone（s）in the event of public emergency，including alarm signals，public evacuation guidance and commands issued by relevant authorities on site，etc..
2.0.5 Business announcement
Announcement released by the PAS to its service zone（s）for the whole or part of the audience，including notices，news，voice files，information，paging and chiming，etc..
2.0.6 Background broadcast
Broadcast released by the PAS for rendering a certain atmosphere，including background music and background sounds（such as environmental simulation sounds in variety occasions），etc..
2.0.7 Loudspeakers distribution
The planning of the specific positions of loudspeakers and the construction of loudspeakers mounting in a PA service area.
2.0.8 Transmission line
Lines that used for transmitting PA signals from station or other signal processing equipment（including amplifiers）to onsite loudspeakers in the service zone（s），such as various conductive cables and fiber-optic networks，etc..
2.0.9 Transmission distance
Length of PA transmission line from the input terminal to the load terminal.
2.0.10 Rated transmission voltage
Rated voltage at the original terminal of PA transmission line，i.e.the nominal input voltage of PA loudspeaker（or some other terminal devices）connected to the PA transmission line.
2.0.11 Ensured function（ENF）
The most basic function that PAS shall be available.
2.0.12 Airing priority
Priority of a broadcast signal.
2.0.13 Microphone priority
Enabling a microphone the highest airing priority.
2.0.14 Voice file
Broadcast voice recorded in advance.
2.0.15 Dual function system（DFS）
One of the standby modes of emergency broadcast system，which runs as a business announcement system or background broadcast system in standby time，and can be switched to emergency broadcast system automatically by emergency trigger signal.
2.0.16 One touch ready
Enabling the system to a specified mode by one touch.
2.0.17 Paging
Broadcast for seeking person，things or help，or for broadcasting temporarily to the designated zone（s）as required.
2.0.18 Call station
Device used for zone paging independent of the broadcast host.
2.0.19 Override
Overriding other signals being on-air with specific contents or awakening the standby system forcibly for releasing emergency broadcast.
2.0.20 Zone management
Dividing a PA service area into several zones for management，all zones or each zone can be turned on or turned off as needed.
2.0.21 Zoning with matrix mode
Zone management in matrix mode for allowing different signals to be broadcast in different zones simultaneously.
2.0.22 Zoning override
An operation that overrides one or more broadcast zones selectively without affecting other zones.
2.0.23 Remote control and monitor
Controlling and monitoring a PAS outside the station（or control center）.
2.0.24 Ensured sound pressure level（ENSPL）
Mean value of the root mean square（r.m.s.）sound pressure level（SPL）at steady-state which shall be available in PA service zone.
2.0.25 Sound field irregularity
Maximum difference of SPL values measured in PA service zone.
2.0.26 Leak out acoustic attenuation
Difference of the ENSPL and the SPL 30m outside the border of the PA coverage area.
2.0.27 System signal-to-noise ratio（system SNR）
SNR of the PAS presenting at the PA loudspeaker's exciting point.
2.0.28 Speech transmission index（STI）
Physical quantity representing the transmission quality of speech with respect to intelligibility.
2.0.29 Speech transmission index for public address（STIPA）
Index obtained by a condensed version of the STI method but still responsive to distortions found in room acoustics including PAS.
2.0.30 Transmission frequency response
Amplitude frequency response of the SPL at measuring points in the PA service zone relative to the input signal level of the system at normal running state.
2.0.31 Passive terminal
Terminal without power supply.
2.0.32 Active terminal
Terminal with power supply.