1200DD Series Digital Data Display Manual
Revision 1.8
1200DD - 2-3
Devices on the Ethernet network continually monitor the receive data path for activity as a means of
checking that the link is working correctly. When the network is idle, the devices also send a link test
signal to one another to verify link integrity. The 1200DD rear panel is fitted with two LEDs to monitor the
Ethernet connection.
10/100
This Amber LED is ON when a 100Base-TX link is last detected. The LED is OFF when a
10Base-T link is last detected (the LINK LED is ON). Upon power-up the LED is OFF as
the last detected rate is not known and therefore defaults to the 10Base-T state until rate
detection is completed.
LN/ACT
This dual purpose Green LED indicates that the 1200DD has established a valid link to its
hub, and whether the 1200DD is sending or receiving data. This LED will be ON when the
1200DD has established a good link to its supporting hub. This gives you a good indication
that the segment is wired correctly. The LED will BLINK when the 1200DD-GPS is sending
or receiving data. The LED will be OFF if there is no valid connection.
2.1.3. Serial Port Connections
COM
This female 9 pin D connector is used for connecting a computer to upload firmware to the
1200DD. It is also used as a diagnostic port for troubleshooting. See section 4.3 for
information on upgrading the firmware.
Pin #
Name
Description
1
2
TxD
RS-232 Transmit Output
3
RxD
RS-232 Receive Input
4
5
Sig Gnd
RS-232 Signal Ground
6
7
8
9
Figure 2-6: COM Port Pinout
GPS
A 9 pin female 'D' connector is provided for connection to the optional GPS receiver (1200DD-
GPS version). Figure 2-7 shows the pinout of the serial port. See section 2.4 for information
about mounting and connecting the GPS receiver.