General Accounting Office, A Comprehensive Review of Optical Character Readers Used in Mail Processing (June 14, 1984) (not available online).
The GAO discussed its comparison of the two optical character reading technologies available to the Postal Service for its automated mail system. The single-line optical character reader (OCR) reads the city, state, and ZIP code line of an address and prints a bar code representing the ZIP code, which is read by other sorting equipment. The multiline OCR reads an entire address and prints a bar code representing the ZIP code. If the address is in the machine's internal directory, the multiline OCR can obtain the ZIP code if none is present.
The GAO stated that the multiline OCR performs better at all usage levels tested and that use of the multiline OCR would result in greater work-year savings than those obtained by use of the single-line machine. However, the difference in savings is not substantial and the GAO believes that it would be less expensive to buy and maintain single-line OCRs. In addition, the GAO believes that a switch to multiline OCRs would delay automation by 3 to 4 years and would result in reduced savings.
The GAO also discussed the feasibility of designing a retrofit kit to convert single-line OCRs to multiline. While such a conversion is technically feasible, the performance level that could be achieved is unknown and could only be determined by designing and testing a retrofit kit.