the step s3 lastly the display presented by the display unit 3 is changed over to the television picture from the television receiver body 5 at a step s8 after which control is terminated by performing control in this manner the display screen of the display unit 6 can be utilized effectively in comparison with the case where both the television receiver and the display unit are turned off in the foregoing description a mobile telephone unit is installed in an automobile however portable telephones have also appeared on the market as a result of recent technological progress if the user is within a telephone service area such a portable telephone can be carried about freely and can be used anywhere and at any time for wireless communication naturally a portable telephone of this type can be carried into an automobile and used while the automobile is traveling as in the case of the mobile telephone unit mentioned above the influence that a portable telephone has upon other wireless receiver units such as a television receiver cannot be ignored therefore it is desired that these other wireless receiver units be controlled in a manner similar to that of the first embodiment an embodiment capable of dealing with a portable telephone is illustrated in fig3 in which portions similar to those shown in fig1 are designated by like reference characters and need not be described again in fig3 numeral 21 denotes a portable telephone.