PCS

PCS, in the US, stands for Personal Communications Services.  It is a frequency band at approximately 1.9 GHz that is intended primarily for digital cellular communications.  One could argue that defining the PCS band of frequencies as digital only would be a moot point, since in 1990 and later when PCS became popular, analog cellular was on its way out and digital were the only new systems going in - at least in the US.

Note that some advertising campaigns have implied that PCS technology means something great and is beyond cellular.  No.  The carrier frequency is often not that important in wireless - as long as the signal is high enough and low enough in frequency to transmit far and there is enough frequency bandwidth for the job at hand.  Car telephone in fact had existed at a number of frequencies before PCS came along, including frequency bands at 150 MHz, 450 MHz, 800 MHz, 900 MHz, and 1.8 GHz.  So a new band at 1.9 GHz is a new band, and not really a new invention.  However, what PCS did do, is open up more frequency space that could now allow even more consumers in the US to use cellular phones at the same time and not interfere with each other.  So, PCS had more business implications one might say than technical feature implications.