AeroComm CL4424 - Manual (Page 13)

CL4424 User’s Manual
6/21/2005 13
Figure 7- DCE to DCE Interface
Note: The Straight Through Cable provided with the CL4424 has female connectors on both
ends and the Crossover cable has a male connector at one end and a female connector at the
other end. Please use a male-to-male adapter or female-to-female adapter wherever required.
Using a null modem adapter with a Crossover cable is equivalent to using a Straight Through
cable.
2.2 RS-485 (2-wire Half Duplex)
The RS-485 interface uses a Differential Data Transmission that can help nullify the effects of
ground shifts and induced noise signals that can appear as common mode voltages on a
network.
The CL4424 implements a RS-485 (2-wire Half Duplex) multi-drop interface. Typically, a RS-485
bus will consist of a master and several slaves. The nodes will have unique addresses and can
send addressed packets to specific nodes. Because the bus is half duplex, no two nodes should
try to talk at the same time. The CL4424 does not have a RS-485 address, therefore, it will
transmit all RS-485 traffic over the RF. Conversely, as soon as a CL4424 receives a packet over
the RF, it will transmit the packet over the RS-485 bus.
Note: When using RS-485 (2-wire Half Duplex), a RS-485 to RS-232 converter is required to
configure the unit. AeroComm recommends a B&B Electronics 4WSD9R converter to translate
RS-485 to RS-232.
CTS
DCE
DCE
Crossover Cable
CTS
RTS RTS
RXD TXD
TXD RXD
GND GND
DCD
DTR
DSR DSR
DCD
DTR
OEM Host CL4424 Modem
NC NC
RI NC RI NC