Garmin plotter - ACC

[simonl]

I have a Garmin 172C baby chart plotter. I'm tidying up my wiring & noticed it has a wire labelled 'ACC' Anyone know what it is? Here's some possibilities.

1. Permanent +ve input to help retain memory?
2. Permanent +ve input so that the voltage monitor isn't affected by the (albeit minimal) current drawn by the device. i.e. a 'sense' wire?
3. Switched output to enable downstream devices when turned on?

I went to the Garmin manual, which are always pretty good. It's got all the wires, except this one! I was surprised.

[Xk59D]

I believe it is to power up other devices when you turn your garmin on, I.e the vhf or another plotter that is connected to nmea