Abstract: A body of a car stereo has a first substrate and a detachable grille has a second substrate. The second substrate has an operating device, a display and a control unit where an identification data is stored. The first substrate has a grille attachment detecting device a power supply means and a control unit having an identification data discriminating device which discriminates the identification data in the control unit on the second substrate of the grille. When the identification data discriminating device determines that an appropriate grille is attached, the power is fed to the grille through the power supply device.

Abstract: A map display apparatus for displaying a wide area map and an enlarged map is disclosed. When a display mode is shifted from the mode of displaying the enlarged map to the mode of displaying the wide area map, a cursor frame is displayed on a position on a parent screen corresponding to the divided area which has been displayed in an enlarged manner just before the shift of the display mode, so that the position on the parent screen of the area which has been displayed in the enlarged manner so far can be easily discriminated.

Abstract: A display apparatus for a multidisk player including a memory for storing data of titles and disk kinds for a plurality of disks, and a controller for reading all the stored data and displaying the title and the disk kind of each disk on a display in accordance with the read data. Accordingly, a user can acknowledge the content of each disk at a glance without actually playing the disks. Furthermore, the user can conveniently distinguish an audio disk from a ROM disk and select a desired one of these disks.

Abstract: The present invention is directed to a structure in which an operation panel is removably provided on the front surface of a housing having a recording-medium playing mechanism provided therein, so that when the operation panel is separated from the housing, the recording medium is ejected from the housing and a recording medium insertion opening is closed when the recording medium is pulled out, or the opening is closed after the recording medium is reloaded in the case where the recording medium is not pulled out.

Abstract: The invention relates to a bidirectional communication line buffer apparatus in which the communication direction of data of a bidirectional data line and the length of the data are judged. A bidirectional buffer circuit receives the results of such judgement and is made non-conductive on the basis of a data termination indication obtained from the received judgement after data is conducted in the communication direction based on the received judgement. Accordingly, the communication data waveform shaping and the driving capability are improved.

Abstract: A polling system for use in an audio system in which a plurality of controllers for controlling a plurality of input/output devices of the audio system and a system controller for controlling the status of the plurality of controllers are connected via a bus line. In an initial polling operation upon power-up of the system, the system controller in order confirms the connection of the plurality of controllers to the system and stores the results of confirmation. When the absence of connection of the controllers is confirmed in the initial polling operation, the system controller further monitors the level on a transmission line provided in the bus line for transmitting a requesting signal from the plurality of controllers to the system controller, and performs the polling operation once more if the presence of the requesting signal is confirmed.

Abstract: An electronic volume control circuit in which the volume setting can be finely controlled, regardless of the level of the input signal, and the output sound level can be rapidly changed. A digital signal is produced indicative of either the duration of up and down instruction signals or a number of times of occurrence of the up or down instruction signals. This digital signal is decoded in accordance with a look-up table to produce data indicative of an increase or decrease width of the volume data. An arithmetic circuit operates in response to the output of the decoder to increase or decrease the volume data according to the up and down instruction signals, and the attenuation or amplification of the input signal is established accordingly.