output at the terminal q 1 becomes high level at the time t 2 in fig2 turning off the lamp 6 upon turning off the lamp 6 the output at the terminal q 1 which has been high level becomes low level in consequence a negative pulse is applied to the monostable multivibrator 7 to make the output at its terminal q 2 low level accordingly the transistor tr 2 conducts and an oscillation current flows from the oscillator osc via the transistor tr 3 to the piezoelectric buzzer 8 to energize it the time during which the buzzer 8 rings is the time t 3 t 2 that is determined by a time constant based on the values of the resistor r 3 and the capacitor c 3 by manually turning the recording switch 3 to off when the piezoelectric buzzer 8 rings a recording error can be stopped if it is desired to keep on shooting it is sufficient only to depress the reset button 10 by which the monostable multivibrator 7 is reset to stop the piezoelectric buzzer 9 from ringing an auto stop device 11 is comprised of a monostable multivibrator 12 having a resistor r 5 and a capacitor c 5 transistor tr 4 tr 5 and tr 6.