User manual

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2270 Fiber Optic Modem
3.7 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-H for pinouts).
NOTE: Only local controls are supported.
Table 3-H. 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.