56
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.
1PPS VALID IN
Set DIP switch 7 on if you want to use the 1PPS VALID IN line as an
external control input (in this situation you would also normally set DIP
switch 8 on). An internal pull-up resistor to 3.3V is provided on this input,
because it is designed to interface with the QS
2
RSU. The maximum
voltage on this input is 9V, and the line must be pulled to ground to indicate
a valid 1PPS signal. The line is activated when released from ground. The
input has no effect if a GPS alarm has already been activated.
When activated, this line can disable the 1PPS outputs. Set DIP switch 3
off if you want to disable the 1PPS RS-485 output. Set DIP switch 4 off if
you want to disable the 1PPS TTL output.
The
1PPS VALID
LED on the rear panel will go off whenever this line is
activated.
Table 4.2
DIP switch settings with an external GPS receiver
Switch
Description
State
Function
1
off
default
2
on
default
3
a
controls the 1PPS RS-485
output on
PORT B
on or off
the 1PPS output is disabled when the GPS fix is lost
4
a
controls the 1PPS TTL
output
on or off
the 1PPS output is disabled when the GPS fix is lost
5
off
default
6
off
default
7
controls the 1PPS VALID
IN input line
optional
on
the 1PPS VALID IN input is enabled
(could be used if an external signal is required to
control the 1PPS outputs - see
“1PPS VALID IN”
below)
off
the 1PPS VALID IN input is disabled
8
sets the signal type for the
1PPS VALID IN and 1PPS
VALID I/O input lines
optional
on
the 1PPS VALID IN signal is steady state
off
the 1PPS VALID IN signal is pulsed
a. GPS alarms have no control over the T801-4 1PPS outputs (via DIP switches 3 and 4) because the Dalman external
GPS receiver is preset to disable its 1PPS output when it loses its GPS fix. Refer to
“1PPS Outputs” on page 33
for
more information.
