The interval between each GPS position logged is set by a factory setting of 15 seconds, but can be changed to other values. The power button can be pressed again to stop the GPS logging, and then again once more to start a new track. It's best to stay still as long as the device finishes first acquisition phase if not that will be extended and the first GPS points can then be dispersed over several kilometers (observation practice when used by car). Once GPS position is acquired the unit begins logging position, time and certain other data to built-in non-volatile memory and the green light stops blinking and glows continuously. During this process the LED on the top blinks green. When switched on the logger immediately proceeds to acquire a GPS fix which takes about 40 seconds from a cold start. The unit requires 2 AAA batteries to operate, which can be 1.2V NiMH rechargeable cells.