Rs-232C And Rs-422 Operation; Figure 2-3 Abx-3 And Mbx-3 Connectivity, Rs-422 - CSI Wireless ABX-3 Reference Manual

The following figure illustrates this requirement for a
GPS receiver operating at the RS-422 communications level:
Figure 2-3 Receiver Connectivity, RS-422
For successful communications, the baud rate of the beacon receiver
must be set to match that of the GPS receiver. Refer to Section 4.8.1
for instructions set the MBX-3 baud rate using the display and keypad,
and Section 5.7.2 for information to change the baud rate of either the
ABX-3 or MBX-3 using proprietary NMEA commands.

2.3.6 RS-232C and RS-422 Operation

A majority of GPS receiver products communicates at the RS-232C
level, similar to a PC computer. However, there are a number of chart-
plotting devices, incorporating GPS capabilities, that operating at the
RS-422 interface level. The default communication level of the ABX-3
and MBX-3 is RS-232C.
To switch from the default RS-232C communication level, you must
remove the MBX-3's front and back panels to slide the receiver board
out of the case approximately two inches. You do not need to remove
the face-place of the ABX-3. Always observe proper electrostatic
discharge precautions (ESD) when handling the beacon receiver or its
components, outside of the enclosure. Such precautions include
proper grounding of personnel, tools, and the surface upon which the
receiver rests.
ABX-3 / MBX-3 Reference Manual
ABX-3/MBX-3
Pin 1 - Tx +
Pin 7 - Rx +
Signal Ground
Pin 5 - Gnd
Pin 2 - Tx -
Pin 4 - Rx -
GPS
Rx +
Tx +
Gnd
Rx -
Tx -
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