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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 159

requiredV.35orX.21standardandinthecaseofSwitched‐56providesdialingcapability.(Some

havekeypadsandLCDdisplaysforthisfunction;othersrelyuponexternalcomputercontrol.)

ThedesignationDSUismostoftenusedwhenterminatingSwitched‐56lines.ModularDSU'sare

alsousedwithinaMultiplexertobreakoutthevariouspaths.Ori

ginally,theCSUandDSUwere

separatepiecesofequipment.Todayhowever,theequipmentsoldforuseonDDSlinesis

nearlyalwaysanintegratedpieceofgearvariouslyreferredtoasaCSU,DSU,CSU/DSU,ora

DSU/CSU.

?

DEEP TECH NOTE!

In the old days a CSU (Channel Service Unit) was used to terminate the digital circuit (to use

the generic term, it was the NCTE or Network Channel Terminating Equipment).

One or more DSUs (often in the form of plug in cards) were used to provide the interface to

the terminal equipment. These days the 2 devices are nearly always combined and are

variously referred to as CSUs, DSUs, CSU/DSUs, and DSU/CSUs! We prefer CSU/DSU and

will use that term.

NotethattheTeloswebsite(www.telos‐systems.com)includesaglossaryifyouneedhelpwith

anyoftheotherterms.

Cables

TheZephyrXstreamconnectstodigitaltransmissionchannelsviatheportsfromtheV.35/X.21

interfacemodule.

ThecablesavailablefromTelos,connecttostandardterminaladaptersorCSUs,which,intur

n,

connecttothedigitalnetworkchannels.Thedesignoftheportelectronicspermitsinterface

witheitherV.35orX.21equipment–theconnectorstyleandpin‐outistheonlydifference.

X.21

Use

Telos Part

# 2091-00024

V.35

Use

Telos Part

# 2091-00023

You can tell whether you have V.35 or X.21 by looking at the connectors. These are the “footprints”

of the two types to help you select the proper Telos cable to interface to your datacom gear.

EachV.35/X.21connectionconveysbothsendandreceivedigitalsignals.

TheV.35orX.21cablefromTelosincludestwoV.35orX.21plugs.Thistwo‐portcablemaybe

usedforsingle‐portapplicationsbysimplylettingtheunusedplug(usuallyport1)go

unconnected.

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