Filter
Top Products
DETAILED CONFIGURATION & REFERENCE | 71
5.11 System Signal Flow and Audio Processing
Send Audio Processing
e Nx12’s send-to-caller audio processing consists of the following functions:
Sample rate conversion
♦
High-pass filter ♦
Frequency shifter ♦
Send AGC/Limiter ♦
Sample Rate Conversion
AES and Livewire sources are sample rate converted to the Nx12’s internal sample rate of 8kHz.
All inputs are re-clocked to the Nx12’s internal clock (derived from the ISDN clock if at least
one ISDN BRI is present).
High-Pass filter
A high pass filter with a 300Hz break frequency improves hybrid performance and enhances
intelligibility by removing unnecessary low-frequencies from the input audio. is function is
always enabled.
Frequency Shifter
A Telos innovation, the frequency shifter (pitch shifter) inserts a small, unnoticeable, shift in
frequency to the send audio to prevent feedback buildup when the system is used with open
speakers.
Send Automatic Gain Control / Limiter
is AGC helps maintain consistent audio levels to the caller. is function is always enabled.
is benefits from a carefully-crafted algorithm utilizing a feed-forward topology with near in-
audible artifacts below the limit threshold. At moderate levels it is ‘AGC-like’ while at high peak
levels it is ‘limiter-like’. In addition to making levels more consistent to callers, this performs the
protection limiting required to meet Telecom regulations.
Receive (Caller) Audio Processing
e Nx12’s receive audio processing consists of the following functions:
High-pass “hum” filter
♦
Duck
Control
X
X
Receive
AGC
DDEQ
SRC
SRC
Fdbk
Reduce
Send
AGC
A/D
AES
D/A
AES
Adaptive FIR
-
HP
Filter
Input Level
Output Level
ISDN
Telco
Analog
Telco
LW
100BT
Analog
Hybrid