Xerox 6180N Generic MICR Fundamentals Guide  - Page 79

Document processing Types of reader sorters The following recognition technologies have been incorporated into MICR reader sorter devices. Waveform reader sorters Waveform reader sorters measure the magnetic signal waveform or pattern of the MICR character as the documents pass the read head. Waveform reader sorters are often referred to as "single slot" or "single gap" readers because the read head contains one magnetically sensitive slot or gap, which covers the height of the entire character string in the clear band. Each MICR character that passes the read slot produces a waveform signal. This signal is compared against the known waveforms of the MICR character set to determine which character was read. Waveform reader sorters are also called "DC readers," because they use a constant magnetic field to magnetize the characters. Waveform reader sorters are generally low to medium speed reading devices. The reject rates for these readers is slightly higher than for matrix readers. Matrix or AC reader sorters Matrix readers use a series of small read heads that are stacked in close proximity, each of which reads a small strip of the character string. The segments of the MICR characters register as binary magnetic flux transitions at each read head. These pulses are combined and used to build a two dimensional bitmap for each character. This bitmap is then compared to known bitmap patterns to determine the identity of the character. To simplify bitmapping, readings from groups of heads are logically combined to produce a single value. This slightly increases sensitivity to spots, but results in lower reject rates for matrix readers. Matrix readers are also called "AC readers," because they use an oscillating magnetic field to magnetize the characters. These oscillations cause a series of waveform peaks in a character stroke, which are recorded as a binary 1 in the bitmap image of the character. Generic MICR Fundamentals Guide 5-5