Visual recording device for e.g. industrial surveillance - passes easily erasable surface over eraser and then over recording device

摘要

The visual recording device is typically in the form of a barograph, or for logging speeds and other parameters of locomotives, lorries etc. It utilises an easily erasable surface, which is passed continuously over the eraser, and then over the recording device. The image remains on the surface until it passes over the eraser again. Paraffin-treated coloured paper can be used as the surface, or alternatively thin tracing paper protected by transparent plastic, eof 'magic slate' form.