Long time standby time battery, with SOS alarm; Portable GPS tracker, easily ... sms: "Warning! Battery is low, please charge in time!" When battery is too low to approach power off, ... 10s, it will enter voice monitoring status. At this time, caller can monitoring the sound in vehicle. Remark: ... The sim card should activate GPRS function. GTK920 long standby time tracker with sos button, handheld tracker