In General Packet Radio (GPRS) cellular radio networks, the multislot service class determines the number of time slots in each direction, with each time slot supporting a theoretical transmission rate of 21.4 kbps. Of the 12 classes, the simplest is service class 1, which supports one timeslot in each direction. The most capable is service class 12, which supports four time slots in each direction. See also cellular radio, GPRS, time slot, and transmission rate.