The surveillance and control of the broadcasting activity, especially in the HF band, is a difficult task for the authorities like the post-office for example. Even experienced people with modern special equipment are often unable to classify unknown, differently modulated signals in real time. In this paper a procedure is described which allows an automatic real time classification of the following modulation types: Amplitude-Shift Keying (ASK), Frequency-Shift Keying (FSK) with small frequency deviation, and Phase-Shift Keying (PSK). The procedure has been tested by simulation on a computer and has proven to be reliable and robust against the expected perturbing factors such as noise, mismatch of centre frequency or bandwidth, and cross-talk of signals in adjacent frequency channels. A more detailed discussion is contained in [1].