Abstract: The Radio Data System (RDS) protocol promulgated by the European Broadcasting Union provides for alternate frequencies (AF) for the same broadcast. Receivers periodically switch over to such an alternate frequency, leading to momentary crackling noises. In a radio receiver having a device for temporary switchover from a received frequency to some other frequency, substitute signals are inserted into the audio signals that are interrupted during the temporary switchover. The substitute signals are formed from the audio signals before and optionally also after the temporary switchover.

Abstract: To simulate presence of a traffic information signal in a traffic information receiver which is muted upon reproduction of tape cassette programs or operated at a predetermined level, a momentary-operating control button is connected to a timing circuit to establish a timing interval which, when exceeded, provides a signal to a traffic information transfer switch to transfer the signals received from the receiver through the traffic information channel to permit setting of the volume level under traffic information conditions as desired and to demonstrate the operability under such conditions; upon release of the button, the system reverts to reproduction of tape or traffic information signals received by the receiver. Traffic information can thus be simulated even though no traffic information is being radiated by the transmitter to which the receiver is tuned.

Abstract: After a preliminary differentiation, the demodulated signal is supplied in parallel to a peak rectifier and to a second differentiating network, the outputs of the latter two circuits being added in the input circuit of a switching transistor that controls the blanking gate of a receiver. The value of the resistor across the output capacitor of the peak rectifier, as well as the rectifier capacitor, is so chosen in value that periodically recurrent pulses that may be persistently present in the signal build up a blocking bias on the switching transistor reducing its sensitivity and preventing corresponding differentiated pulses from switching it on, whereas occasionally or irregularly appearing pulses develop a negligible bias through the rectifier, so that their twice differentiated derived pulses will switch on the transistor and produce blanking.