190-01639-00 GSU 75 ADAHRS Installation Manual
Rev. 6 Page 4-8
4.5 GSU 75 OAT (Outside Air Temperature) Probe
The OAT probe connections are used to power and interface with a GTP 59. Temperature input is used for
Outside Air Temperature (OAT) computations. The temperature input is a three-wire temperature probe
interface. OAT Power Out and OAT High are connected internally at the OAT probe. A GTP 59 or other
supported temperature probe is required for the GSU 75 installation. The GTP 59 is a Resistive
Temperature Device (RTD). Refer to Figure B-1
for the temperature probe interconnect.
4.6 GSU 75 PPS (Pulse Per Second) Inputs
The GSU 75 supports both a single ended and a differential PPS signal from the GPS. The single ended
PPS input accepts a 0/5V CMOS logic-level signal. The differential PPS input conforms to the electrical
specifications of the EIA standard RS- 422 receiver.
PPS SELECT (pin 25) determines which PPS mode is used. PPS SELECT connected to GPS PPS IN 1B
(or 2B) input selects single ended mode. PPS SELECT (pin 25) floating (unconnected) selects differential
mode. The mode is determined by the source of the GPS PPS signals (generally Nav Radios).
Table 4-13 GSU 75 OAT Probe I/O
Pin Name Pin I/O
OAT LO 4 In
OAT HI 5 In
OAT POWER 6 Out
Table 4-14 GSU 75 PPS Inputs
Pin Name Pin I/O
PPS SELECT 25 In
PPS IN 1A 60 In
PPS IN 1B 40 In
PPS IN 2A 41 In
PPS IN 2B 61 In
The document reference is online, please check the correspondence between the online documentation and the printed version.
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