stocker for example m 0 indicates that carriage s is in use and that stocker 14 is at position s m 1 indicates that carriage 1 is in use and that stocker 14 is at position 1 and m 6 indicates that carriage 6 is in use and stocker 14 is at position 6 a memory device not illustrated for storing the current status of d 0 through d 6 and m is backed up by a lithium battery to prevent the stored information from being destroyed when the power source of player 100 is turned off referring to fig1 and 9a through 9d when the power source of player is turned on player 100 performs routine steps s1 through s5 to detect an eject load signal e i a play mode signal play a carriage s selection signal s or a carriages 1 6 selection signal 1 6 when stock switch 41 is manipulated the stock goes from h to l and step s1 becomes yes an n becomes 1 in a step s6 and disc numbers d 1 through d 6 are searched sequentially to determine the presence of discs in carriages 1 through 6 if any carriage is empty step s7 becomes yes and optical head base 11 is moved from the up position to the down position in a subroutine l1 referring to fig1 and 10 when subroutine l1 is initiated cl down signal goes from l to h and optical head base 11 is lowered in a step s10 when.