A system, apparatus and corresponding method by which to synchronize to a
time reference a main module of a device--a main module such as global
positioning system (GPS) receiver--using a cellular communication signal
received by a cellular module also included in the device. To synchronize
the main module to the reference time, the invention provides a method
including the steps of: having the cellular module respond to the
cellular communication signal by providing to a clock module of the main
module a trigger pulse derived from the data component of the cellular
communication signal, and also by providing to the main module
information relating the trigger pulse to a universal time. The main
module is then able to resolve a value for time based on the information
relating the trigger pulse to a universal time and the trigger pulse.