Abstract: Objects on a delivery conveyor are detected by a photo-detector connected to a multi-bit shift register which is clocked by a pulse generator connected to the delivery conveyor. A NOR gate is connected between two outputs of the shift register and the shift register resets to erase information relating to undersized objects. Another circuit having NAND gates connected to a series of shift register outputs and to a counter connected to the pulse generator determines the presence of objects over a base size. A comparator connected to the counter provides a signal to a microprocessor, connected to the shift register resets, to erase information relating to an oversize object. Another section connected to the intermediate output of the shift register detects the location and length of gaps between adjacent objects. This section provides information to the microprocessor which through its connections to the shift register erases information relating to the leading object if the gap is too small.