A device and a method for operation of railway track circuits are disclosed, which have an associated section length which is restricted at both ends by track isolation. The following procedure is used for reliable identification of the states of FREE, BUSY and DISTURBED within a predetermined time limit. A transmitted signal is fed into the rail body at one of the two section ends. The received signal is output at the opposite end, and is passed on for analysis. The transmitted signal that is fed in is sinusoidal. The frequency is switched cyclically between two discrete values. Three evaluation channels are operated at the receiving end. The information is A/D-converted for all three channels. Two channels have a bandpass input filter, which is matched to pass the channel (1) with the frequency that is currently being transmitted, for the other channel (2) with the frequency which is not being transmitted. The busy state is detected by the channel (1). The currently occurring disturbance influence is measur
