I only worked with GSM. One of our competitors at the time was Sprint and they used CDMA. I did some testing of prototype phones that supported AMPS, TDMA and

I only worked with GSM. One of our competitors at the time was Sprint and they used CDMA. I did some testing of prototype phones that supported AMPS, TDMA and CDMA, but they attached to their respective networks and used GSM on our network. Most of the prototype phones never saw the light of day.