PURPOSE: To always display a bar graph on an image receiving tube so that a start position of the bar graph can be indicated clearly, by generating a pulse having prescribed pulse duration even if an audio input signal is not supplied.
CONSTITUTION: An audio signal which has come in from an input terminal 1 is supplied to a pulse duration transducer 4 through plural filters 2 connected in parallel, and plural rectifying and smoothing circuit 3, is compared with comparison voltage 13 and is converted to a pulse duration signal corresponding to its level. This pulse duration signal is time-divided in order in the horizontal scanning period by a multiplexer 5, is fetched serially, is supplied to an image receiving tube 8 through an adding gate 10, and is displayed as a bar graph. This comparison voltage 13 is set so as to exceed "0"V in a prescribed time in one vertical scanning period, therefore, even when voltage to be compared, by the transducer 4 is "0"V, a start position of the bar graph is displayed on the image receiving tube 8. In this way, correspondence of the bar graph and a character displayed on its lower stage is grasped easily.
TANAKA YOSHIAKI
OOTSUKI YOSHIKI
