The present invention relates to a radio inter-face for a cordless small system using the 2.4 GHz ISM band. According to the present invention, a transmission system having a fixed station (1) and at least one mobile station (2, 3) is provided for this purpose, the fixed station (1) and the mobile station (2) each having devices (RF modules 4, 5) in order to transmit the data in time slots using a frequency-division multiplex method (FDMA) and a time-division multiplex method (TDMA), and with time division duplexing (TDD). As is known from DECT Standard, the data are modulated onto a carrier frequency (fx) using a GMSK modulation method. The RF modules (4, 5) in the fixed station (1) and, respectively, the mobile station (2) are in this case designed such that the carrier frequency (fx) is changed after a predetermined time period, which may correspond, for example, to the time duration of a time slot or of a transmission frame. A transmission frame in this case contains 16 time slots.