The basic function For GSM Payphone as below ; 1.Single display with call meter 2.850 / 900 /1800 /1900 mhz frequency 3.Use with solar panel or external recharge 3 days battery 4.Network management 5.Lock keyboard 6.Call records - 170 incoming calls and 20 missed calls 7.Add prefixal code automatically 8.Locking telephone, locking sim card, locking service provider and locking district 9.Handfree - needn't lift the handset 10.Receive or send short message