GPS
What is GPS, or Global Positioning System?
The U.S. government set up GPS to make it possible to determine position information anywhere on the globe. Most people think of GPS for use in navigation devices, but the GPS signal also contains very accurate time information.
GPStimers uses the time and location information to determine local time in its products. Some timing products use pager or cell phone signals. But these signals don't reach everywhere, and they may require a subscription fee. GPS is available worldwide for free.
GPStimers Products and GPS Signals
GPS signals are stronger near windows and in higher levels of a building. You may have to move the GPStimers products closer to a window or to a higher floor to receive GPS signals. In a hilly or mountainous terrains, it is possible that the GPS signal will be blocked altogether by higher ground. GPS signals don't travel well through metal enclosures, either.
GPStimers products indicate 1) whether they can receive any GPS signal, and 2) whether they can receive adequate GPS signal to establish local time. See product information printed inside the cover of the GPStimers product you own for instructions on indicator lights. If the timer clock shows the local time in 5-10 minutes, you have adequate GPS signal strength. In general, if the product cannot receive adequate GPS signals in your desired location, try moving closer to an external wall or higher in the structure. If you have problems receiving signals outside, try moving higher up a slope or towards a space with a larger view of the sky.
GPStimers products also remember the last known location they were in before a power interruption. If you want to install a GPStimers product in a place with weak GPS signal strength (where the indicator for GPS signal indicator lights up but the clock does not set itself after 30 minutes), try the following procedure. Plug in or power up the timer in a location that 1) has adequate GPS signal strength to set the GPStimers device clock to local time, and 2) is within a few miles of your desired location. Never plug in an In Wall Timer device into a standard electrical socket unless it has been professionally wired to a plug. Then unplug the device and plug it in to or install it in your desired location. The GPStimers product may find enough signal strength in your desired location to reset its clock to the correct local time even though it cannot determine its current location. If this procedure does work, remember that the timer will use the last known location rather than the current location to determine sunrise and sunset times as well as daylight savings time settings.
If you are an electrician or installer who installs the GPStimers HD500 In Wall Timer and you have access to a standard electric receptacle nearby the desired installation location, you may want to test GPS signal strength with the GPStimers HD100 Plug In Timer before installing the in wall timer. Also, you may want to set the last known location in the GPStimers HD500 somewhere close to the installation site where you know there is adequate GPS signal strength (for instance, your office) before you leave for the installation. That way, even if there is a not adequate GPS signal to determine the location at the desired location, the GPStimers HD500 will have a last known location stored to use when it determines sunrise, sunset, and daylight savings time settings.
For further discussion of GPS, please see the Wikipedia page