Blaupunkt-werke Gmbh

Reinhard Wieschhoff

Peter Seibold

Hubertus Pagany

Andreas Rinne

To suppress tuning noise interferences, and particularly transients, such as whistles and the like, especially in FM receivers during returning of the receiver, an inter-station retuning muting circuit is, in accordance with the invention, modified by including therein a switchable filter (2) having a low-frequency cut-off (f.sub.g2) which is higher than the frequency of noise interference due to retuning of the receiver, the filter being switched to the higher frequency cut-off level for a period of time (T.sub.E) which exceeds the normal muting time (T.sub.E) of FM receivers.

Circuit and method of suppressing inter-station radio tuning noise

To permit cooling of transistor push-pull bridge-type audio end stages in car radios, where heat dissipation and cooling of components is difficult to achieve, without entire interruption of signals being amplified, the temperature of a heat sink (HS) is being sensed by a temperature sensor (14), and, if a predetermined level is exceeded as determined, for example, by a threshold circuit (15), one of the bridge arms formed by a transistor (10) is controlled to become saturated, thereby grounding-out the applied signal, so that a loudspeaker (6) will operate at only half voltage and hence 1/4 power, to thereby permit cooling of components, while providing some reproduction of introduced audio signals from an audio input terminal (11).

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Hildesheim, Germany

Reinhard Wieschhoff