ROC364 Instruction Manual
4-6 Communications
Cards
Rev
Jun/05
4.2.4 Leased-Line Modem Communications Card
The Leased-Line Modem Communications Card is a 202T modem that is FCC part 68 tested for use
with leased-line or private-line telephone networks. Refer to Figure 4-4. Two- or four-wire, half- or full-
duplex asynchronous operation is supported at a software selectable 300, 600, and 1200 baud to Bell and
CCITT standards.
LED indicators on the card show the status of the RXD, TXD, DTR, DCD, CTS, and RTS control lines.
LED indicators are detailed in Table 4-1 on page 4-3.
The Leased-Line Modem Communications Card has three jumpers (P3, P4, and P5) that permit either
two-wire or four-wire operation. Use connector P7 signals for monitoring or connecting to an analyzer.
Refer to Section 4.3.1, Setting Modem Card Jumpers, on page 4-10 for more information.
The output attenuation can be reduced, as necessary, to better match the modem output to the line or
radio. Plugging a resistor into the card at R2 makes the adjustment. Refer to Section 4.3.2, Setting
Modem Card Attenuation Levels, on page 4-11.
Refer to Section 4.4.4, Leased-Line Modem Communications Card Wiring, on page 4-16.
DOC0246A
R6
R17
CR7
CR8
T1
R23
C15
C17
C16
R13
R14
R21
R22
R19
R18
U9
U10
R7
R1
1
R1
2
R8
R9
R1
0
U4
FB4
Y1
C2
6
C2
9
R2
5
C2
8
C27
LEASED LINE/RADIO MODEM
COM PORTS
U5
R24
C8
CR4
DCD
CR6
CR5
RP
1
RT
S
CT
S
RP
2
CR3
CR2
CR1
TXD
DT
R
R
XD
U6
U7
FB5
C2
3
C2
4
C25
C22
FB6
Y2
C1
8
W1
C11
C10
C1
2
C14
C1
3
R20
R16
R15
C5
U1
FB1
C1
C6
FB2
FB3
30
2
1
J1
30
2
1
P1
C7
R5
C4
R2
6
R1
C2
U2
ISO
2W
4W
2W
4W
2W
4W
GND
C9
U3
4
P4
P5
P6
4
2
2
4
P3
2
4
2
R2
30
2
1
J2
1
2
30
P8
3
P7
7
5
1
C19
VR6
VR5
U8
C20
C2
1
VR2
VR1
T2
VR3
VR4
1
P2
Figure 4-4. Leased-Line Modem Communications Card
LED Indicators
P3 Jumper
P7 Connector
P4 Jumper
P5 Jumper
R2 Attenuation