2 model -22, 3 model -h22, 4 model -r2r – CANOGA PERKINS 2270 Fiber Optic Modem User Manual
Page 25: 1 model -22 3.3.2 model -h22 3.3.3 model -r2r, D rs-449 (rs-422) signals and pin assignments
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2270 Fiber Optic Modem
Table 3-D. RS-499 (RS-422) Signals and Pin Assignments
pin
EIA
signal name
CCITT
signal direction
1
FG
Frame Ground
101
frame ground
19
SG
Signal Ground
102
signal ground
4/22
SD
Send Data
103
to modem
5/23
ST/SCT
Send Timing
114
from modem
6/24
RD
Receive Data
104
from modem
7/25
RS/RTS (b,c,d,e)
Request To Send
105
to modem
8/26
RT/SCR
Receive Timing
115
from modem
9/27
CS/CTS (d,e)
Clear To Send
106
from modem
10
LL/LT (a)
Local Loopback Test
141
to modem
13/31
RR/DCD (e)
Receiver Ready /
Data Carrier Detect
109
from modem
14
RL/RT (a)
Remote System Test
140
to modem
17/35
TT/SCTE
Terminal Timing
113
to modem
11/29
DM/DSR
Data Mode/Data Set
Ready
107
from modem
a.
The 2270 & 2290 Modems include a built-in Loopback Test feature. Two normal test lines (RS-423 pins 10 and 14)
are used for this interface loop. Refer to Chapter 5, "Troubleshooting," for a more thorough description of this
feature.
b.
Model -22: Request To Send is held low when there is no connection or the interface connection is removed.
c.
Model -H22: Request To Send is held high when the user's device does not supply an RS input or the interface
connection is removed.
d.
Model - R2R: Request To Send is held low as with the -22. Clear To Send is provided as a balanced output.
e.
Only local handshake is supported.
3.3.2 Model -22
The RS input control is biased to the OFF (negative voltage) state. If a connection is not made to
this line, the CS control output from the modem will drive to the OFF state.
3.3.3 Model -H22
The specific difference between the -H22 model and the standard -22 model is that the RS input
control is biased to the ON (positive voltage) state. If a connection is not made to this line, the CS
control output from the modem will drive to the ON state.
3.3.4 Model -R2R
The RS input control is biased to the OFF (negative voltage) state. If a connection is not made to
this line, the CS control output from the modem will drive to the OFF state.
This interface provides the Clear to Send (CS) control as balanced output (i.e. the "B" lead (pin 27)
is active rather than at signal ground).