Polycom Vortex EF2241 Reference Manual page 62

EF Bus
Equalization
Line Echo
Macros
Matrix Mixer
Noise
Cancellation
NOM
NOM Attenuation
NOM Bus
Presets
Room Gain
V EF2241 Reference Manual
ORTEX
The EF Bus is a digital bus that includes the W, X, Y, and Z audio busses as well as
the echo canceller reference and remote control information. It can be used to link
multiple Vortex devices.
Equalization is the process of adjusting frequency characteristics of an audio signal.
Line echo is caused by reflections of the audio signal from the telephone hybrid. The
EF2241 is an example of a device that includes a line echo canceller.
An arbitrary set of commands that can be replayed.
A matrix mixer allows you to choose which inputs are included in each output. Some
matrix mixers allow you to assign crosspoint gains to the inputs.
Noise cancellation is a digital signal process that removes noise from an audio signal
corrupted by real-world interferences such as HVAC, office noise, crowd noise, or
road noise. Generally, there are two parts of a noise cancellation algorithm: a method
to detect the noise and a method to remove the noise. The Polycom noise cancellation
algorithm (patent pending) is capable of removing 10 dB or higher of noise with no
degradation at all to the resulting speech signal. This method does not attenuate
speech, and removes noise during both speech and idle periods.
NOM refers to the number of open microphones in a system.
NOM attenuation is the gain applied to the overall system gain to the microphone sig-
nals to compensate for how many microphones are open. The amount of attenuation
is calculated by 10*log (NOM).
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A NOM bus carries signal information as well as NOM information (i.e., the number
of open microphones in the system, NOM).
Presets correspond to configuration parameters that have been previously saved to
EEPROM.
The room gain of a conferencing system refers to the relative levels of the signal sent
to the line output to your amplifier (before any amplification) and the level of this sig-
nal that is reflected at the microphone input (after microphone amplification). If the
electrical level of the reflected signal picked up by the microphone is the same as the
level of the electrical signal sent from the AEC to the line output to your amplifier, the
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