MANUAL P/N 900000025 REV A
10
3.3.1 Alarm Input Connection
The IBU-240 may be used with an external reference such as the Brandywine
Communications GPS8 or PTS system that incorporates a discrete alarm signal.
This alarm signal is used to indicate that there is a fault (e.g. GPS not tracking)
on the reference signal even though the time code input signal may be present.
The factory standard IBU-240 configuration is a logic HI signal on the ALARM IN
pin indicates that the input is GOOD. A built in pull-up resistor ensures that if no
ALARM IN connection is made, the reference is still considered good. To
change the polarity of the ALARM IN, remove the top cover of the IBU-240 and
set the links to the link settings seen in the tables shown below.
LINK SETTING
REFERENCE A STATUS
LK1 2-3
HI – reference A is GOOD
LK1 1-2
LO – reference A is GOOD
LINK SETTING
REFERENCE B STATUS
LK2 2-3
HI – reference B is GOOD
LK2 1-2
LO – reference B is GOOD
