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Telos Zephyr Xstream Two-Way Radio User Manual

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USER’S MANUAL

Section 9: The V.35/X.21 Interface Option 163

InthedirectionCSU/DSU‐>ZephyrXstream,onlyCD(CarrierDetect))isimplemented.This

signalisusedtotelltheZephyrXstreamwhichport/channelhasbeenconnectedandactivated.

Itisusedforinternalselectionofthenetworkclocksource.WhentheTELmenuselection

Interfaceissetto“V.35”theTE

Lstatusscreenwillindicate“Inactive”or“Active”dependingon

whethertheCDsignalispresentforthatchannel.NOTEthatatanygiventimeonlyoneofthe

V.35signalsisprovidingclockwhichisusedforbothports.ThereforebothV.35sourcesmust

beatthesameclockfrequency(wh

ichisgenerallythecasesinceTelco’susehighlyaccurate

clocksourcesforalloftheirgear).



Configuring CSU/DSUs

Therewillgenerallybeatleasttwomainconfigurationmenus.OneforinterfacetotheDTE

(DataTerminalEquipment)andonefortheinterfacetothe“loop”or“line”.YourCSU/DSU

manual(o

rmanufacturer)shouldhaveinformationonthecorrectsettingsforthevarious

options.

DTE Options:

Setto“Synchronous”andsetthebitratetomatchtheZephyrXstream’sandline’sbitrate

(usually56kbps).Ifnecessary,youmaydisableanyhandshakingsignalsbysettingthemto

“forced”or“ignored”sincehandshakingisnotrequiredwithsynchronousdata

.“Anti

streaming”or“scrambling”optionsshouldbedisabled.

Loop or Line Options:

Settothespeedofyourline(usuallyeither56or64kbps).TheXstream’sCODECmenuoption

BitRatemustbesettothesamerateastheline.YourTelcoorCSU/DSUmanualshouldbeable

togiveyouth

ecorrectsettingforanyotheroptions.

Clock Options:

Itisessentialthattheclockoptionbesetto“network”or“fromloop”.TheXstreamwillclockits

synchronousdatatotheclockfromtheCSU/DSU.Inordertopreventbufferoverflowor

underflow,thefarendunitmustsharethesamecloc

k.Theonlywaytoensurethis,isforeach

CSU/DSUtoderiveitsclockfromthenetwork(i.e.fromthelineitself).TheCSU/DSUmustnot

deriveclockfromtheV.35port.

t

DEEP TECH NOTE!

In cases where "dry line" modems are used one end can use a local clock (master) and the

other end (slave) can derive timing from the far end by using loop timing.

If a dual port scenario is to be used with these modems, the second modem at the master end

would need to be slaved using the clock connections on the V.35 ports of these two units. It

can be done, but you will need to fabricate a special cable to do so.

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