Privacy as well as capacity is improved in digital cellular. Snoopers with scanners easily listen in on analog cellular signals. Eavesdropping on digital transmissions is more difficult, however, because the digital bits are scrambled when they are sent. Even though it is more difficult to listen in on digital conversations, though, privacy is not guaranteed. Sophisticated digital scanners can be used to listen in on cellular digital calls. Nevertheless, digital scanners are more expensive than analog scanners. They are also not as readily available. Many vendors of digital scanners claim that they sell them only to law-enforcement agencies.
Handsets for digital cellular have both an analog and a digital mode; they are dual mode. When callers roam into areas without digital cellular, their calls are automatically put into analog mode. Newer cellular phones now operate in trimode: in GSM, TDMA, and analog cellular markets. New Nextel phones now operate on the Nextel airwaves in the United States as well as the GSM service offered internationally. Thus, people with these phones can use them seamlessly in some international locations. VoiceStream phones can also be used internationally. However, the VoiceStream network is not as ubiquitous in the United States as that of other carriers such as AT&T Wireless, Sprint PCS, and Verizon Wireless.