5902 Bell 202 Modem Hardware Manual
October 19, 2007
11
Pin
Type
Description
Pin 6
DSR
output
This signal indicates the modem is ready to start
communication. It is always in a MARK state.
Pin 7
RTS
input
This input must be a MARK for the modem to transmit
data. The DTE should set it to a MARK just before
transmission of data. The CTS output will be asserted
when the modem is ready to transmit data.
The RS LED is ON for a MARK level.
Pin 8
CTS
output
This output indicates the modem is ready to transmit data.
A MARK level indicates the modem is ready. The DTE
should wait for this signal before transmitting data.
The CS LED is on for a MARK level.
Pin 9
5 Volt
Power
input/
output
This pin is connected to the 5V power supply. It is a power
source for an external device when used as an output. It
powers the modem when used as an input.
This pin must NOT be connected if it is not used.
All RS-232 wiring must use shielded cable. The shield should be connected to chassis ground at one
end of the cable only. The DE-9 connector shell is a good ground point. Failure to properly shield
the cable may result in the installation not complying with FCC or DOC radio interference
regulations.
The 5902 modem is connected typically to a DTE device.
Figure 3: RS-232 Wiring - 5902 (DCE)
to DTE
shows a typical connection.
The serial cable that is provided with the 5902 modem is suitable for connecting the modem to a
Data Communication Equipment (DCE) device.
DTE
5902 (DCE)
6
9
DCD
RxD
TxD
DTR
GND
RTS
CTS
5 Volt
2
3
4
5
7
8
1 DCD
RxD
TxD
DTR
GND
RTS
CTS
See device
specifications
for pin numbers
Pin 9 is a connected to the 5 Volt
power supply. Use caution when
connecting to this pin.
Figure 3: RS-232 Wiring - 5902 (DCE) to DTE