THEORY of OPERATION
The transcription process may essentially be split into two distinct tasks. These are Recording and Processing.
The first operation is to record the data contained on the typewriter ribbon.
The principal of operation of the RAW system depends, for successful analysis, on the ribbon being transported at a controlled speed from one spool to another in front of the light unit which illuminates the ribbon for the camera. The system uses the movement of the ribbon and successive camera images to capture and reproduce the full image of the characters from the ribbon. These images are built up and stored on the computer hard disk.
To enable rapid re-tracing of important sections of the ribbon, a positional marker is recorded along with the image data. This allows, if required, further processing to take place at specific sections of the ribbon chosen by the operator.
Once the ribbon has passed through the system, processing of the captured data may take place. Depending on the laboratory working practices, the ribbon may be removed from its spacer for storage with other evidence until, or if, it is required again. Alternatively, it can be left on the machine for re-winding to play back specific areas should secondary checking of the ribbon be necessary.
Before processing may commence, the system must be taught the basic layout of the text on the ribbon. Parameters learnt during this stage are the number of rows of text on the ribbon (1, 2 or 3) and the direction in which they appear (bottom left/top right or top left/bottom right).
Along with a number of software filters available to ensure that even broken characters may be treated as valid, the operator has the option to impose “Ignore Windows” around consistently damaged areas of the ribbon. These windows are generally applied for the removal of ribbon damage caused by Star-wheel mechanisms which are used by some manufacturers to aid pull-through of spent ribbon
It is important to note that due to the way in which the character data is recorded, the RAW is able to process and print out non-Roman characters, including Japanese and Cyrillic alphabets, together with mathematical and technical symbols.
Processing of the ribbon data may take a number of forms. Under most circumstances the operator will chose to produce a print-out of the whole contents of the ribbon. This will be set out in a format which shows all the characters as they would have appeared on the original typed page with the absence of spaces, carriage returns and paragraphs.
Since all ribbon text is held in magnetic media form, once recording is complete, a further alternative is to simply store the data until a suitable time slot is allocated or the case reaches priority status before completing the transcription process and printing out the results.
The current model of the RAW system was completely redesigned during 2003/4 in order to make use of more modern components which could be supported into the future.
At the same time as the electronic redesign, the software was completely rewritten, primarily to bring it up to date and once again ensure that it was supportable.