INTER-MUSIC DETECTING CIRCUIT OF AUTOMATIC MUSIC SELECTION RECORD PLAYER

PURPOSE:To prevent malfunction due to a different record disc size and malfunction due to music-selection by providing a gain switching circuit of an amplifier or a reference voltage switching circuit of a comparator so as to detect surely the edge of record disc. CONSTITUTION:Since a switch 15 is turned on when an inter-music sensor 11 is placed at a reference position at the outer circumference of the record disc, an output Q of a RS flip-flop 14 goes to L, a feedback resistor of the amplifier 12 is only a resistor 18 and the gain is increased. In moving the inter-music sensor 11 in the direction of record edge, the switch 15 is turned off, and when an output pulse corresponding to the record edge is outputted from the comparator 13, the RS flip-flop 14 is inverted, a resistor 17 is connected in parallel with the resistor 18 and the gain of the amplifier 12 is decreased. Thus, while the inter- music 11 is placed in the vicinity of the outer circumference of the record disc, the gain of amplifier is kept higher and after the 1st pulse is detected at the record edge, the gain of amplifier is decreased.