<P> After 2G was launched, the previous mobile wireless network systems were retroactively dubbed 1G . While radio signals on 1G networks are analog, radio signals on 2G networks are digital . Both systems use digital signaling to connect the radio towers (which listen to the devices) to the rest of the mobile system . </P> <P> 2G has been superseded by newer technologies such as 2.5 G, 2.75 G, 3G, and 4G; however, 2G networks are still used in most parts of the world . </P> <P> With General Packet Radio Service (GPRS), 2G offers a theoretical maximum transfer speed of 50 kbit / s (40 kbit / s in practice). With EDGE (Enhanced Data Rates for GSM Evolution), there is a theoretical maximum transfer speed of 1 Mbit / s (500 kbit / s in practice). </P> <P> 2G technologies can be divided into time division multiple access (TDMA) - based and code division multiple access (CDMA) - based standards depending on the type of multiplexing used . The main 2G standards are: </P>

Second-generation (2g) wireless networks transfer data at a rate of ____