I think that, in another post, Peter CRDC confirmed that the SB5 is just the solenoid within that you will want to look at - i.e. its the "CF3" cutout.

It paired with a C35A dynamo with an external box resistance on it... the external box became part of the cutout and became the CFR.

So care when pairing units as you might not have enough things to make everything work if you get the wrong dynamo!

the Dorset diagrams are good. Good to hear the Cornforth is improved.... minor clarification on the PLC switch makes it even easier to understand. And the new drive-thru MacDonalds between the F1 - F2 bridge is a great idea!