68
System Configuration
T801-4 Installation and Operation Manual
© Tait Electronics Limited September 2007
DIP Switch Settings
Set the DIP switches on the rear panel as indicated in the following table.
Some switches have optional settings, depending on the requirements of
your particular system. Refer to
“DIP SWITCHES” on page 22
for full
details of all the DIP switches.
Table 4.7
DIP switch settings with dual QS
2
RSU receivers
Switch
Description
State
Function
1
selects the external 1PPS
RS-485 input on
PORT B
on
on
enables the external 1PPS RS-485 input on
PORT B
;
configures the 1PPS VALID I/O signal line on port B
as an input
off
disables the external 1PPS RS-485 input on
PORT B
;
enables the internal GPS receiver
2
selects the RSU GPS
receiver
off
on
the 1PPS RS-485 input from the secondary RSU is
active (top
GPS SELECTED
LED)
off
the 1PPS RS-485 input from the primary RSU is
active (bottom
GPS SELECTED
LED)
3
controls the 1PPS RS-485
output on
PORT B
disabled
by link
W400
disabled in this configuration because the 1PPS RS-485
output is configured as an input
4
a
controls the 1PPS TTL
output
on
on
the output is always enabled
b
(ensures the 1PPS
output is restored after a changeover)
off
the output is disabled when one (or both) of the
1PPS signals from the RSUs becomes invalid
5
on
default
6
selects the GPS changeover
alarm trigger
off
on
the GPS receiver changeover is disabled
off
the GPS receiver changeover is triggered by the
1PPS VALID inputs
7
controls the 1PPS VALID IN
input line
on
on
the 1PPS VALID IN input is enabled (for a valid
signal from the secondary RSU)
off
the 1PPS VALID IN input is disabled
8
c
sets the signal type for the
1PPS VALID IN and 1PPS
VALID I/O input lines
optional
on
the 1PPS VALID signals are steady state
off
the 1PPS VALID signals are pulsed
a. Refer to
“Setting DIP Switch 4” on page 69
for more information on setting this switch.
b. If the QS
2
RSU has version 3.00.00.00 and later firmware, the 1PPS output may be invalid or disabled during the
≈
28 second delay before changeover occurs. This depends on the nature of the fault in the GPS receiver which
initiated the changeover. Refer to
“1PPS Outputs” on page 33
for more details.
c. You must set DIP switch 8 off if you are using a QS
2
RSU with version 3.00.00.00 and later firmware because the
RSU provides a pulsed VALID signal (1 pulse/10 seconds). Set DIP switch 8 on if you are using a QS
2
RSU with
firmware earlier than version 3.
