ROC364 Instruction Manual
4-5 Communications
Cards
Rev
Jun/05
4.2.3 Radio Modem Communications Card
The Radio Modem Communications Card sends and receives full-duplex or half-duplex, asynchronous
Frequency Shift Keyed (FSK) signals to the audio circuit of a two-way radio. The modem incorporates a
solid-state push-to-talk (PTT) switch for keying the radio transmitter. Refer to Figure 4-3.
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.
Jumper P6 determines whether the PTT signal is isolated or grounded. 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 4.4.3, Radio Modem Communications Card Wiring, on page 4-15.
C18
U7
Y2
U6
U5
1
2
30
P8
30
2
1
J2
U10
U9
R23
LEASED LINE/RADIO MODEM
C27
R24
R25
C26
CR6
Y1
RP1
RT
S
RP2
C28
COM PORTS
C29
FB5
C25
C23
C24
C22
FB6
P7
3
5
7
1
R20
R16
R6
R15
R18
R19
R22
R21
C17
CR8
CR7
R17
30
2
1
P1
U3
U1
2W
2
C9
30
2
1
J1
FB3
FB2
FB4
C8
C6
C5
U4
CR1
CR2
CR3
CR4
CR5
TX
D
DCD
CT
S
DT
R
RX
D
C7
C11
C10
C13
C14
W1
C12
GND
4W
4W
2W
4W
2W
ISO
R10
R9
R12
R7
R8
R11
4
2
4
P6
C16
R14
R13
C15
P5
4
2
P4
4
2
C1
FB1
U2
R1
R2
C2
C4
P3
R26
R5
T2
T1
C19
U8
C20
C21
VR6
VR5
VR4
VR3
VR2
VR1
P2
1
DOC0247A
Figure 4-3. Radio Modem Communications Card
LED Indicators
P6 Jumper
P7 Connector
R2 Attenuation