8 ccitt v.35 interface model -35, J ccitt v.35 digital interface and pin assignments – CANOGA PERKINS 2270 Fiber Optic Modem User Manual
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2270 Fiber Optic Modem
3.8 CCITT V.35 Interface Model -35
This interface is compatible with CCITT recommendation V.35 Appendix II (electrical characteris-
tics for balanced double-current interchange circuits).
The RTS control input is biased to the OFF state. If a connection is not made to this line, the CTS
control output will drive to the OFF (negative voltage) state. Recommended cable is a twisted
multi-pair type with a characteristic impedance of 80-120 ohms at the operating data rate. The
balanced line receivers are terminated at 100 ohms.
The V.35 interface uses a standard 34-position, M-series (MRAC-34S) Winchester connector. The
terminal or computer interface must be configured as Data Terminal Equipment (DTE) for proper
communications handshake (refer to Table 3-J for pinouts).
NOTE: Only local controls are supported.
Table 3-J. CCITT V.35 Digital Interface and Pin Assignments
pin
mnem
signal name
CCITT
signal direction
a/b
A
FG
Frame Ground
101
n.a.
B
SG
Signal Ground
102
n.a.
C
RTS
Request To Send
105
to modem
D
CTS
Clear To Send
106
from modem
E
DSR
Data Set Ready
107
from modem
F
DCD
Data Carrier Detect
109
from modem
R/T
RXD
Receive Data
104
from modem
V/X
SCR
Serial Clock Receive
115
from modem
Y/AA
SCT
Serial Clock Transmit
114
from modem
P/S
TXD
Transmit Data
103
to modem
U/W
SCTE
External Transmit Clock 113
to modem
CC (*) RL/RT
Remote System Test
140
to modem
HH (*) LL/LT
Local Loopback Test
142
to modem
n.a. = not applicable
(*) = The 2270 Modem includes a built-in System Test feature. Two normal test lines (CCITT V.35 pins CC and
HH) are used for this interface loop. Refer to Chapter 5, "Troubleshooting," for a more thorough description of
this feature.