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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 157

9.3 Hook-Ups to Non-ISDN Synchronous Networks

The V.35/X.21 Connection

Ifpresent,theV.35/X.21interfaceissuppliedinslotBslot,lookingfromtherear.Itpermits

connectiontotransmissionpathsotherthanISDN.ItmayalsobeusedwithexternalISDN

TerminalAdaptersinthe(rare)casewheretheavailableISDNserviceisnotcompatiblewiththe

Zephyr’sinte

rnalTA,orforemergencies.

?

CURIOSITY NOTE!

You might wonder why the much more common RS-232 is not used. Answer: V.35 is

synchronous, meaning that the bit clock is transmitted between the two ends.

RS-232 is typically used for self-clocking (asynchronous) applications, and requires overhead

start and stop bits, slowing and chopping the bit flow. And, just as with audio, balanced

transmission is more reliable in a noisy environment, or in one which has ground potentials

at differing levels.



V.35isastandardforconnectingtosynchronousdigitaldatapaths.LikeRS‐232,itdefines

signalsand(notofficially)connectorsandpin‐outssothatequipmentfromvarious

manufacturersmaytalkwitheachother.TheusualconnectorisabigboxyAMPtype,which

waschosenbyAT&Tdecadesago.Mo

stterminalequipmentsoldfortheUSmarketsupports

theV.35standard(althoughanadaptercablemayberequiredtoconnecttotheusual

connector).ThefollowingSignalsareprovidedattheV.35endoftheTeloscable:

V.35 CONNECTOR PIN-OUT

Pin Description Direction (Xstream ◄► DCE)

B Ground

C # RTS (Request to Send) ►

F CD (Carrier Detect) ◄

H # DTR (Data Terminal Ready) ►

P * TX Data ►

R RX Data ◄

S * /TX Data ►

T /RX Data ◄

V RX Clock ◄

X /RX Clock ◄

Y TX Clock ►

AA /TX Clock ►

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