Abstract: An RDS or RDBS radio broadcast receiver, utilizing a microcontroller and a serial communication bus, receives a list of alternative frequencies to allow the receiver to switch to an alternative frequency when the quality of the main radio broadcast signal deteriorates. Therefore the quality of the alternative frequency transmissions has to be updated from time to time. To avoid time delays caused by the relatively slow serial communication bus, the tuning section includes further controller for performing the alternative frequency updates.

Abstract: For the extension of busses use is made of special bus driver and receiver circuits which are capable of charging or discharging the higher capacitances of longer bus lines more quickly. However, in such circuit arrangements the direction is reversed by means of special control signals so that data transmission always takes place always in only one direction; or in other known circuits the reversal is liable to give rise to interference signals. In accordance with the invention, each bus of a local sub-system is connected to the control input of a transistor, notably a PNP-transistor whose collector is connected to 0 V and whose emitter is connected to the extended bus and, via a resistor, to +U. Moreover, between the emitter and the base there is connected a resistor which represents the pull-up resistor for the signals produced on the bus, the signals arriving via the extended bus are coupled onto the bus of the sub-system via this resistor.