hints for IET GCHQ readers puzzle October 2017

Checking forward and transposed reading of the coordinates coded in rational expression of the circuits wrapping the GCHQ puzzle published on the cover of Institute of Engineering and Technology (IET http://theiet./org) publication October 2017 attachment Early Careers.
Even with Texas Instruments TINA Spice simulator building the simple blocks was taking too long. The efficient way to obtain the equivalent resistor values in rational expression is with pen an paper.

The puzzle is also published here

https://www.gchq.gov.uk/news-article/gchq-and-iet-present-new-puzzle-designed-stem-students-and-apprentices