Monday, October 17, 2005

EEF comes up with the goods on Laser Printer embeded codes

from the above link:
Each column is read top-to-bottom as a single byte of seven bits (omitting the first parity bit); the bytes are then read right-to-left. The columns (which we have chosen to number from left to right) have the following meanings:

* 15: unknown (often zero; constant for each individual printer; may convey some non-user-visible fact about the printer's model or configuration)
* 14, 13, 12, 11: printer serial number in binary-coded-decimal, two digits per byte (constant for each individual printer; see below)
* 10: separator (typically all ones; does not appear to code information)
* 9: unused
* 8: year that page was printed (without century; 2005 is coded as 5)
* 7: month that page was printed
* 6: day that page was printed
* 5: hour that page was printed (may be UTC time zone, or may be set inaccurately within printer)
* 4, 3: unused
* 2: minute that page was printed
* 1: row parity bit (set to guarantee an odd number of dots present per row)

gleaned from boingboing

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