Telos Hx1 - 4 Configuration Settings; Sample Rate Conversion

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4 Conguration Settings
Conguration of the Hx is done via DIP switch settings. ere’s a quick reference guide in the
back of this book that lists the remote connector pin numbers and all of the available congura-
tion options and their switch settings. You’ll probably use those two pages more than anything
else in this manual. ere’s also a diagram at the end of this section that shows inputs, outputs,
controls and metering points. A picture is worth a thousand words, maybe more when you’re in
a hurry.
Before we lose you to the “quick reference guide” we should point out that here we provide the
details that you might need to set up your Hx most eectively. If this is your rst Hx, a few
minutes with this section will help you determine which features will help you in your particular
application.
Send Audio Processing
e Hx1 and Hx2 hybrid’s send-to-caller audio processing consists of the following functions:
♦ Sample rate conversion
♦ High-pass lter
♦ Anti-Feedback - the “pitch” shifter and Acoustic Echo Canceler
♦ Send AGC/Limiter
Sample Rate Conversion
AES and analog input sources are sample rate converted to the hybrid’s internal sampling rate
of 8 KHz.
High-Pass lter
A high pass lter with a 300 Hz break frequency improves hybrid performance and enhances
intelligibility by removing unnecessary low frequencies from the input audio. is function is
always enabled.
Send Automatic Gain Control / Limiter
e AGC helps maintain consistent audio levels to the caller. is function is always enabled. At
moderate levels it is ‘AGC-like’ while at higher peak levels it is more ‘limiter-like’. In addition
to making levels more consistent to callers, it performs the protection limiting required to meet
Telecom regulatory requirements.
Feedback Reduction
e HX has a simple Acoustic Echo Canceler (AEC) that improves feedback performance and
cancels echo caused by ‘speaker to mike’ acoustic coupling. e HX also uses a ‘frequency shifter’
(a Telos innovation) that inserts a small, unnoticeable, shift in frequency to the send audio to
prevent feedback buildup when the system is used with open speakers.