V.35 Bus



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V.35 Bus Description and Pinout

V.35 bus was discontinued and replaced by the V.10 / V.11 standards in 1989.
The V.35 interface supported 48kbps over an RJ45 telco connector.
The speed for V.35 was later increased to 2Mbps.
At 48kbps the maximum cable length is around 400 meters, and at 2Mbps the maximum length decreases to 15 meters.
The pin out below is for a 34-pin square connector (MRAC-34).
V.35 uses differential signaling (V.11) on the data and clock lines, while control signals are Single-Ended (V.28).
The characteristic impedance is 100 ohms, With differential voltage levels employed at +/- 1.1 volts DC.
Off-set from ground is +/-0.2v at the driver and +/- 0.6 volts at the receiver.
Note the usage of a metal frame or chassis ground is not that common with cable interface standards.





V.35 Pinout and Signal Descriptions
Pin Name Pin ID Pin Description Signal Type
FG A Frame/Chassis Ground Ground
SG B Signal Ground
SDA P Send Data A Differential
SDB S Send Data B
RDA R Receive Data A
RDB T Receive Data B
RTS C Request To Send Unbalanced
CTS D Clear To Send
DSR E Data Set Ready
DTR H Data Terminal Ready
RLSD F Received Line Signal Detect
TCEA U Transmit Clock Ext A Differential
TCEB W Transmit Clock Ext B
TCA Y Transmit Clock A
TCB AA Transmit Clock B
RCA V Receive Clock A
RCB X Receive Clock B
LL J Local Loopback Unbalanced
RLB BB Remote Loopback
TM K Test Mode
- L Test Pattern



V.35 Standard Organizations

International Telecommunication Union {ITU}
CCITT is the old name for the ITU standards group

Also refer to the US standard organizations:
Telecommunications Industry Association {TIA}
Electronic Industries Alliance {EIA}, which has now disbanded

V.11: Electrical characteristics for balanced double-current interchange circuits operating at data signalling rates up to 10 Mbit/s

{Back to V.35 Bus Index}


V.35 Bus Interface IC Manufacturers

Exar {Single Chip programmable V.35 Transceiver IC in a LQFP44 package}

Texas Instruments 'TI' {V.35 ICs in SOIC and DIP packages}

Also refer to these pages for interfacing logic:
TeleCom IC Manufacturers
Memory Chip IC Manufacturers
Processor Chip Manufacturers
Glue Logic IC Manufacturers
Of course the driver IC is the chip that functions over the interface.

Design Note;
As of 2011 these devices are still in production, but given the interface age, care should be taken in adapting the interface.





The V.35 interface is certainly out-dated just by the fact of the slow data transfer speed.
Having been superseded by the V.11 interface 20 years ago is also another factor to consider.
It's a bit hard to clam the V.35 interface is obsolete given the fact that interface ICs are still being produced.
However V.35 was replaced and judging by the decline in internet searches in on the decline.
From a relative level of 3 in 2004 to a level of 0.25 searches in 2010, an 8x decline according to Google data.
Of course regardless of V.35's demise, the pin out is tabulated here for debug purposes or historical reference.


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Modified: 3/04/12
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