ROC364 Instruction Manual
4-15 Communications Cards Rev Jun/05
4.4.3 Radio Modem Communications Card Wiring
The following signal lines are used with most radios:
Comm Port Signal Line Description
3 RXA Receive data
4 TXA Transmit data
5 COM ROC power supply ground
7 PTT+ Push-to-talk switch
8 PTT–
Push-to-talk return
(may be grounded)
The radio modem uses jumper P6 to determine the use of the PTT return line. Refer to Section 4.3.1,
Setting Modem Card Jumpers, on page 4-10.
The Radio Modem Card is shipped without a resistor installed in the R2 position. To modify the
attenuation level, select a resistor (R2) as directed by Table 4-3, Radio and Leased-Line Modem
Communications Card Attenuation Levels, on page 4-11.
Figure 4-13 shows the relationship between the radio modem signals and pin numbers for the
communications port 9-pin connector.
Figure 4-13. Radio Modem Wiring Schematic
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