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Telos Zephyr Xstream Two-Way Radio User Manual

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USER’S MANUAL

Section 11: THE WORKS – Detailed Menu Reference 206

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COMPATIBILITY TIP!

When two channels are required for transmission (i.e. for Stereo, J-Stereo, and Mono 128) an

"inverse multiplex" (IMUX) scheme must be used to break the standard MPEG data stream

into two streams for transmission.

In Layer-3, the Zephyr Xstream uses the FHG/Telos Zephyr IMUX protocol. Other Layer-3

codecs support this method, allowing for compatibility among different codec manufacturers.

The Telos IMUX used in AAC and AAC-LD is available on our website to encourage

compatibility with other manufacturers that may choose to support AAC in the future.

AAC‐LDStereo

AAC‐LDJoint

TheseworksimilarlytotheequivalentLayer‐3modes(seeabove).Two

connectionsarerequired.These(andtheotherAAC‐LDmodes)modesare

importantsincetheyoffersignificantlylowerdelaythananymodeotherthan

G.722.

Offers14kHzaudiofrequencyresponse.

AAC‐LDMo

no64

Thisencodesasinglemonobitstream,normallyusingtheaudiofrominputA.

ThisbitstreamisfedtobothISDNBchannelssoitcanbetofeedidenticalmono

totwosites.

Offers14kHzaudiofrequencyresponse.

AAC‐LDMono128

ThisusebothBcha

nnelstransmitasingleaudiochannelusingtheaudiofrom

inputA.BothBchannelsareusedforthebestqualityand"codingheadroom"

laterinthetransmissionpath.

Offers16kHzaudiofrequencyresponse.

AACJ‐stereo64

Thismode,whileitofferingreducedaudiobandwidth,allowsstereo

transmissionoverasingleBchann

el.Theresultingcodedbitstreamisoutput

overbothBchannels(ifdialed)allowingtheidenticalstereoaudiotobesentto

twositessimultaneously).

Offers10kHzaudiofrequencyresponsewhentheSampleRateissetto48kHz

and7kHzaudiofrequencyresponsewh

entheSampleRateissetto32kHz.

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