the dual-sim (gsm+gsm) 3g karbonn a21 is powered by a 1.2 ghz dual-core qualcomm snapdragon processor, and runs android 4.0 (ics). sporting a 4.5" capacitive touchscreen with 480x800 pixels, the handset offers 3g support in sim 1 and 2g for sim2. it works with quad-band gsm (900, 1800, 1900, 2100 mhz) frequencies. the phone comes with 4 gb of internal memory, a 32 gb microsd card slot, 1.3 mp front camera, and 5.0 mp main camera with autofocus and led flash. its 1800 mah battery claims a talk time of 5 hours and about 8 days of standby time. other features include wi-fi, bluetooth, and usb support. - see more at: http://www.techtree.com/content/news/2101/karbonn-android-40-a21-a9-smartphones-starting-9000.html#sthash.jinmvyg8.dpuf
Hard Reset Karbon A21:
Press And Hold Volume Up + Power Key
Now You See Green Screen Dont Release Volume Up Key
After 10 Seconds You See Red Screen, Now Release Volume Up Key.
Now Tou See Recovery Options.
Select Wipe Data With Factory Reset And Press Power Key For 2 Sec.
Now Select Yes And Press Power Key For 2 Second.
Now Reboot Device.
Note: If This Method Note Work Try Below Solution For Hard Reset
How To Hard Reset Karbon A21 Via Android Multi Tool: You Need To Boot Your Phone Into Fastboot (follow Exactly What I Said Bellow) Power Off Phone Pull Out Battery & Insert It Again Press Volume Up + Power Button For 5 Seconds Ur Phone Will Boot Up With Fastboot Now Open Android Multi Tool & Press 8 From Ur Pc Keyboard & Press Enter