, in which individual users transmitted digit- ized, and compressed audio in time-synchronized time slots on a single channel. GSM was a rollicking success: It united European cellular networks under a sin- gle technology, improving production volumes of both handset and base-station equipment, enabling seamless roaming almost worldwide, improving security (digital signals cannot be easily listened in on using a scanner, though GSM is hardly cryptographically secure), and somewhat improving bandwidth effi- ciency compared with analog. The Great Telecom Meltdown North American operators did not jump on the GSM bandwagon. In part this was because GSM was not designed for easy compatibility with AMPS. So second-generation (2G) cellular in the United States and Canada moved in dif- ferent directions. Two standards initially competed for the marketplace. One system, usually known simply as TDMA though more formally as "D-AMPS" or IS-54, and later IS-136, used a different variation on TDMA technology to squeeze three calls into each original channel. This was adopted by AT&T Wireless (originally McCaw Cellular, before AT&T purchased it) and SBC's Cellular One, among others. The competing system was based on an entirely different technology, code division multiple access (CDMA), developed by Qualcomm Corp. Based on spread spectrum technology, which spreads many users' signals across a wide frequency band rather than assigning different fre- quencies to each user, CDMA promised greater frequency efficiency, better voice quality, and longer battery life than TDMA. But it was a bit later to mar- ket and costlier to deploy. Bell Atlantic NYNEX Mobile and GTE Wireless (both later merged into Verizon Wireless) and Sprint Spectrum were major GSM adoptees. Both of these digital systems improved network bandwidth effi- ciency enough to allow usage prices to go down while improving profit margins at the same time. 2G also permitted a little bit of data transmission, typically 9,600 bps. This led to a fairly widespread rollout of 