Telos Hx1 - Page 30

22 | Section 4
Receive Audio Processing
e Hx1 and Hx2 hybrid’s receive audio processing consists of the following functions:
♦ High-pass “hum” lter
♦ Adaptive Echo Cancellation
♦ Automatic Gain Control
♦ Noise Gate
♦ Digital Dynamic Equalization
♦ Sample rate conversion
High-pass “hum” Filter
is lter removes hum and other unwanted low frequency noise from the caller audio. is
lter has a break frequency of 100 Hz.
Adaptive Echo Cancellation
An adaptive lter removes studio send audio from the received caller audio. It adapts continu-
ously and naturally.
Receive Automatic Gain Control
e Hx’s smart gated AGC improves the consistency of the caller’s audio level delivered to the
studio console, without audible processing ‘artifacts’ .
An important additional feature of this AGC is that it is cross-coupled to other sections of the
hybrids and can therefore reliably distinguish between caller audio and hybrid leakage. is
allows a more aggressive gain control for bringing up low-level callers while still preserving
excellent hybrid performance.
Noise Gate
Turning on the noise gate enables the built-in downward expander. e downward expander
reduces low level line noise when no caller audio is present and reduces low level leakage. is
function is cross-coupled with the AGC and the ducking system.
Digital Dynamic Equalizer
Telephone audio frequency response varies widely as many dierent factors can aect it (we’ve
measured the response on a number of calls and the results were very revealing). Consequently,
some form of receive equalization is desirable. e Hx’s Digital Dynamic EQ process is the
most sophisticated equalizer available in a broadcast telephone interface. All processing is
performed in the digital domain. e Receive EQ settings control the type of equalization
applied to the receive telephone audio as follows:
♦ O - e caller audio is passed without modication.
♦ Fixed - is is a simple manual equalizer.
♦ Adaptive (Digital Dynamic) - is is a three band dynamic equalizer. We’ve chosen
frequency breakpoints, time constants, and other characteristics to optimize the tonal
quality of varied telephone callers. You set desired ‘target levels’ to customize the callers
spectral characteristics, which are maintained from call to call.
♦ Adaptive + Fixed - is mode separately adds a xed amount of additional gain to the
high and low frequency bands of the three band dynamic equalizer.