The Interface
       

Pinouts and cables for telecomms
  home | contacts | site policy    
   

X.21 / V.11 connector

  
  MENU
CCITT X.21   EIA RS-449 ISO 4903
 
X.21 defines the physical characteristics for a general interface between DTE and DCE using synchronous transmission on public data networks . This interface is extensively used for 64Kb circuits and 56Kb/s (USA and Japan).The interface electrical characteristics comply with CCITT V.11 . It should be noted that these voltages are not compatable with V.35 voltages.  15 way dtype
ISO 4903 assigns the X.21 circuits to a 15 way D-Type connector.
 
CCITT V.11 Pin Designations
CCITT No Pin No DTE --- DCE Description
G 8 ---------------- Signal ground
T 9- , 2+ Transmitted Data
R 11- , 4+ Received Data
C 10- , 3+ Control functions as 108.1 in V.24
I 12- , 5+ Indication functions as 107 in V.24
S 6- , 13+ Signal Element Timing
X.21  can also be presented on a 37 way D-Type connector ISO-4902.
Signal G T+ T- R+ R- C+ C- I+ I- S- S-
15 WAY 8 2 9 4 11 3 10 5 12 13 6
37 WAY 19 4 22 6 24 5 23 - - 26 8
 
     

CCITT V.11   EIA RS-422A

V.11  Specifies voltage levels for BALANCED circuits with speeds up to 50 Mb/s. A typical speed of 10Kb/s over a distance of 1000 Meters on unterminated copper wires and 100Kb/s on terminated copper wires is more usual however. Balanced means each signal has its own return wire.

 

Electrical characteristics for  V.11:

Logic STATE Voltage levels
CONTROL DATA INPUT OUTPUT
OFF 1 < -0.3v -3v
ON 0 > +0.3v +3v
 
CCITT V.10   EIA RS-423A
V.10  Specifies voltage levels for UNBALANCED circuits with speeds up to 100 Kb/s with typical speeds of about 1Kb/s over copper twisted pairs up to 1000 Meters.The V.10 generator circuits have signal conductors with a single common return similiar to V.28.
 

V.10 receivers can be set up with either :

  • Category 1 separate returns for each signal conductor
  • Category 2 one common return for all signal conductors.
 
LINKS
   
  If you find this useful and have information to add email Martin Ryan. All contributions , queries and constructive criticisms are welcome.  
{short description of image}