Toggling of H and 3G Symbols Near the Signal strength in Mobile Phone

If you are using GSM service you may note the toggling of 3G and H symbols in your mobile phone near the mobile signal strength. When the mobile phone is idle (It means no data transfer ), it turns to 3G but if we start Internet activities it will turn back to "H" from 3G. Maybe these symbols confuse a non-techie person. Before explaining this I think it is better to give a short description of data bandwidth technologies we are using right now. 2.5G is known by the term GPRS in data service and 2.75G is termed as EDGE. If you see the "E" symbol while using data service, it is EDGE network your mobile phone is connected. In the same way, "UMTS" technology is commonly termed as 3G and HSDPA is termed as H. However, there is a difference in mentioning 3G and "H". 3G carries both voice and data but "H" is purely data service.

Why showing H in 3G network
So if your handset is HSDPA enabled, it can transfer data up to 7.2Mbps speed in a 3G network. If your handset is not HSDPA enabled the maximum speed limit you can expect is 384 kbps. So when you start data transfer in your mobile phone, it will automatically change to maximum possible speed and the 3G symbol will change to H. When there is no data transfer your phone does not need to continue in H and it will come back to 3G.

However, do not confuse with the original 3.5G network where the data transfer speed limit is 42 Mbps (download limit). If you like to know more about these mobile data service technologies, follow the link below.
Compare EDGE, GPRS, 3G and HSDPA