The Faster Serial Interface.

Basically, V.35 is a high-speed serial interface designed to support both higher data rates and connectivity between DTEs (data-terminal equipment) or DCEs (data-communication equipment) over digital lines.

V.35 is an interface (V.35 is the ITU - formerly CCITT standard termed "Data Transmission at 48 Kbps Using 60-108 KHz Group-Band Circuits") commonly used on higher speed circuits of 56kbps and above. Recognizable by its blocky, 34-pin connector; V.35 combines the bandwidth of several telephone circuits to provide the high-speed interface between a DTE or DCE and a CSU/DSU (Channel Service Unit/Data Service Unit). To achieve such high speeds and great distances, V.35 combines both balanced and unbalanced voltage signals on the same interface. Transmission is usually a synchronous protocol (note clocking pins i.e. receive and transmit clock). Although V.35 is commonly used to support speeds ranging anywhere from 48 to 64 Kbps, much higher rates are possible [ ISDN (64 or 128Kbps), Factional T1 128 Kbps to 1.544Mbps T1, ATM and Frame Relay]. V.35 cable distances theoretically can range up to 4000 feet (1200 m) at speeds up to 100 Kbps. Actual distances will depend on your equipment and the quality of the cable . Lan routers often come equipped with a V.35 electrical interface but many today are using a HSSI interface at speeds higher than T1 and above (typical T3 45Mbps).

V.35 M34 connector to 
DB25 connector

V.35 cable cross-over for tail circuits

V.35 cable cross-over for tail circuits

- Tail Circuit cables are made to order

- Standard pin-out or custom

- 5 day lead time.

V.35 cable 18 pin layout

V.35 cable Pin # Source Description

A - Common Chassis Ground
B - Common Signal Ground
C - DTE Request to Send
D - DCE Clear to Send
E - DCE Data Set Ready
F - DCE Data Carrier Detect
H - DTE Data Terminal Ready
J - DCE Ring Indicator
K - Local Test
L - Unassigned
M - Unassigned
N - Unassigned
P - DTE Send Data A Balanced
R - DCE Receive Data A Balanced
S - DTE Send Data B Balanced
T - DCE Receive Data B Balanced
U - DTE Terminal Timing A Balanced

V - DCE Receive Timing A Balanced
W - DTE Terminal Timing B Balanced
X - DCE Receive Timing B Balanced
Y - DCE Send Timing A Balanced
Z - Unassigned
AA - DCE Send Timing B Balanced
BB - Unassigned
CC - Unassigned
DD - Unassigned
EE - Unassigned
FF - Unassigned
HH - Unassigned
JJ - Unassigned
KK - Unassigned
LL - Unassigned
MM - Unassigned
NN - Unassigned


V.35 cable Connector pin layout