Koso RX2 GP installation question with no key and total loss ignition

Hopefully someone has done this so I do not have to experiment. The instructions say to connect the red wire directly to the positive pole on the battery and the brown wire to the +12v on the key switch. I have a minimal wiring harness and do not have a key so thought that I would just go to the positive pole on the battery as well so I have 12v on both. But then when I read the notes it says that running the red and brown power wires in parallel will cause the meter to work improperly. Does anyone have any ideas on what I will need to do to ensure the meter works correctly when installed?

 

While I haven't worked with this specific setup, I would guess that the brown would connect to the "far side" of the start / stop switch circuit so that it's only getting +12v when the start / stop switch is in the "on"/"run" position (which would be the equivalent of the key switch only providing +12v when the key is on).

If I had to guess on the internal design, the red +12v line is used to provide full power to the system but that power line is only activated when the brown +12v line is enabled. Most ignition switches are low-current and probably can't source enough current to the tach. I suspect that the tach has a power transistor which has the red +12v on the input (source / collector), the brown +12v is the control (gate / base) and the rest of the tach is fed from the transistor output (emitter / drain) - when power is applied to the brown line, it will allow the red line to feed the rest of the tach (all of this is similar to power relays such as a starter relay). This transistor is likely the reason that the notes say that running the red & brown in parallel will cause problems.

 

That was kinda what I was thinking with the brown being the "control" line. The direction I was thinking about going was just running a separate power wire off the main power cable through a switch to the brown 12v power wire and see how that works. Hopefully Koso gets back to me with some clarification but I am not holding my breath...