User's Manual

CSI-Wireless LoCate-001 Users Manual
Revision 1.0 Page 7 6/11/2001
1.4 Operating Modes
The LoCate-001 unit offers two major operating modes.
1.4.1 Armed Mode
When either of the LoCate-001 digital inputs becomes active, the LoCate-001 enters the Armed
mode within 1 second.
The LoCate-001 will enter the Armed Mode based on activity on the analog input
only during the wakeup period. The Armed Mode is a low power mode in which
the only active functions are a wakeup timer and monitoring of the three input
lines (the analog input is monitored only during the wakeup period). The vehicle
battery level is sensed when the unit periodically wakes up to listen for messages
from the LoJack Network Control Center (LNCC). The wakeup duration set by
the configuration must be long enough, and its interval short enough, to account
for Microburst network latencies.
1.4.2 Active Mode
In the Active Mode, the cellular radio is continuously on. Status will be transmitted at the interval
define by the configuration (10 minutes).
2 System Component Description
The following sections provide description of the various system components.
2.1 Twelve Channel GPS Receiver.
The LoCate-001 unit incorporates an integrated twelve-channel GPS receiver.
2.1.1 GPS Position/Velocity Fix.
The GPS receiver establishes a position fix as shown in Table 1.
Time for Fix Certainty Conditions
<< 1min.
90% GPS receiver powered on 6 –24 hrs. without a current
almanac, satellite ephemeris, initial position or
time.
<< 30 sec.
90% “Warm Start”, GPS receiver powered on 1 – 6 hrs. with
a current almanac, satellite ephemeris, initial
position and time.
<< 10 sec.
90% “Hot Start”, GPS receiver powered off for less than 60
minutes with a valid almanac, satellite
ephemeris, position and time.
Table 1 - Establishment of Position Fix
The GPS almanac is updated continuously as pages of the almanac are received
during Active Mode state. During the Active Mode the GPS receiver is always
powered on and attempting position fixes.
The GPS receiver can be configured during the Armed Mode to specify the
“maximum time to fix” interval allowed for the GPS receiver to get a fix before
powering off the GPS. This mode is necessary in situations where the GPS
antenna is completely hidden from the sky and cannot get an updated position fix
during its Armed Mode ‘wake-up/status check’ cycle.