Cables and Pin Assignments
C-7
7975-A2-GB20-40
December 1998
Table C-3.
X.21 Cable Interface
Signal
CCITT
Number
Direction
Pin
Signal Common
102
—
8
Transmitted Data
103
To DSU/CSU
2 (A)
9 (B)
Received Data
104
From DSU/CSU
4 (A)
11 (B)
Request-to-Send
105
To DSU/CSU
3 (A)
10 (B)
Data Channel Received Line Signal
Detector
109
From DSU/CSU
5 (A)
12 (B)
Transmit Signal Element Timing
(DTE Source)
113
To DSU/CSU
7 (A)
14 (B)
Receiver Signal Element Timing
(DCE Source)
115
From DSU/CSU
6 (A)
13 (B)