Digital AMPS (D-AMPS) is a digital mobile telephony system that evolved from the analog AMPS standard. It employs TDMA to divide a 30 kHz analog radio channel into three digital channels, enabling a gradual transition to digital mobile communication. Initially specified in IS-54, it later became part of the IS-136 (ANSI-136) standard. D-AMPS, often referred to as TDMA, operates in both the 850 MHz and 1900 MHz bands, offering voice and data services with a maximum bit rate of 8 kbit/s and a short messaging service (SMS).