I got a couple of solars and im using the electrical engines to charge redstone energy cells. On the left side of the electrical engine is the slot for Circuits. But in the middle is something additional. Looks like a vent/turbine/pump or something - but i cant figure out the usage. Hard to find information about that - can you help me with that?
I sometimes use an electrical engine + my batpack to power fillers in the early game before I get redstone cells
I've been seeing the Mindcrack people use Heating Vents (that are normally used in Nuclear Reactors) in that slot. I dunno if it's actually doing anything or not, as I have not tested it myself, but it might be worth it to try that out.
Mayhaps... No sources I have been able to find have mentioned that usage, but on the other hand it would be weird to have a slot with no use... will test later
Tested it. Two engines side by side toggled at the same time none of the vents effect it. And as a side Totally Soul powered by Saice, on Flickr You can put just about anything in that slot it seems only a battery actually does anything though.
That slot is for cirquit boards. Look under upgrades: http://forestry.sengir.net/wiki/index.php?n=Machines.EngineTin
If I recall correctly, that slot does not do anything, and the symbol is the symbol for "alternating current". Which is a little funny seeing that the system seems to be more of a direct current system, since you can power devices with batteries. I guess you could have an inverter built into all the devices, or just accept that it's a game and not real life... =P
