[sonata149]

Just to make things a bit clearer I attach some images in connection with the above. WRT the Leak circuit diagram, MPX is taken from the bottom end of R33 in parallel with OA79 on V5a (ECF80 pentode section). This can be seen a circuit diagram of the Troughline 2.

Then there are 2 images of the decoder I'm using.

Thanks for your input.
Joe A