PCS is an acronym for Personal Communications Service. This is a term used by the Federal Communications Commission (FCC) to refer to a set of digital cellular technologies being deployed in the United States. PCS includes CDMA (also called IS-95), GSM and TDMA (also called IS-136) mainly used in North America. The frequency of PCS is 1920-1990MHz.
PCS is a network service launched by sprint in the United States. Its predecessor is PTT (PushToTalk), which is a service network mainly used for one-to-many calls. At first, it only had the function of TALK, and later there were value-added services such as voicemail. So it was renamed PTC (PushToCommunication) and now the service is very mature.