indicating that a good read was obtained by the scanning assembly 18 or the multivibrator 98 times out setting of the flip flop 80 will result in the output term siq going high which conditions an and gate 108 for operation upon the tripping of the exit item gate 74 fig2 if this event occurs immediately after the tripping of the enter item gate 54 a signal 1gl generated by the photodiode 42 fig1 over line 109 fig2 to the control logic unit 58 will enable the and gate 108 whose output will enable an and gate 120 and thereby set the flip flop 82 which places the control logic unit 58 in a second state when in the second state the control logic unit 58 is conditioned to either complete the read operation upon receiving a good read signal from the processing logic unit 61 or require the operator to initiate another scanning operation this latter event will occur if such good read signal is not received by the control logic unit 58 within two seconds or whatever time the multivibrator 98 is set to time out or if the exit item gate 74 returns to its uninterrupted state the circuit of the logic control unit 58 returning to its idle state upon the enter gate 54 being cleared of a merchandise item in a manner that will now be described the output term s1q of flip flop 80 as shown in fig3 is also applied to the or gate 110 whose output is applied to one input of the and gate 112 upon the timing out of.