Personal Communications Service (PCS) is very similar to digital cellular, and in some cases the two terms are interchangeable. PCS is a wireless phone service that emphasizes personal service, and it was developed especially for extensive mobility. Both systems operate through a network of cells spread throughout each geographic area. Areas are divided into cells that use different frequencies, so that the user can be traveling -- passing through different cells on the communications network -- and get continuous phone connectivity. PCS also includes other services in the same package, such as caller ID, email and paging.
Cell phones were originally developed for use as car phones. The PCS phone service was designed from the start with mobility in mind. The cells that the network runs on are smaller, with more antennas covering each area. The frequencies PCS uses, 1850-MHz to 1990-MHz bands, are different than the ones that cellular phones in the U.S. typically operate in, which are 824-MHz to 894-MHz. Digital cellular service usually has 30-kHz channel spacing and three time slots, while PCS has 200-kHz channel spacing and eight time slots.
Cell phones have different options for operating modes. Multiple band phones operate in one mode, but they can switch frequencies as needed. Multiple mode phones can switch between modes, for example from TDMA to AMPS (analog). Other cell phone models offer multiple frequency bands and transmission mode options, with the ability to switch transmission types and frequencies automatically. PCS is based on TDMA technology, which is usually the default option for cell phones. Connecting at the 1900-MHz TDMA frequency is usually tried first; phones that support multiple modes will always try digital mode before analog. This is important for people who need continuous uninterrupted phone service while traveling.