Transitional Tagcodes and Routing Codes
This is a translator for the "transitional" codes of the 1990s with a pattern of bars, which were used during the switch to OCR/VCS and before 4-state codes came in. There were three types:
- Full routing codes (lower row, 31 bars): These encode both the inward and outward parts of the postcode.
- Partial routing codes (lower row, 17 bars): These encode just the outward part of the postcode.
- Tagcodes (upper row, 39 bars): These encode information about the machine used and the time of processing.
The general idea is that you match the bar pattern on your cover by clicking on the appropriate bar positions to turn them on or off, and the interpretation appears in the box below. The "Start/Stop" (S) positions were there to provide a fixed point for the machinery to start reading from (working right to left) and bars are always present in those positions. The "Format" (F) positions padded out the patterns and had basically the same effect, again these bars are always present. The "Parity" (P) positions were for error checking – a dot was printed only when needed to make the number of bars in the appropriate section of the pattern even (so a section with an odd number of bars could be assumed to be an error). These positions can be a big help when deciding exactly how many spaces there are between bars ....
The parity bars in this tool will be switched on and off automatically, according to the rest of the pattern.