Thanks. I think I have it now.
Originally Posted by Mike Wilde
I found a manual for the modules on the Butkus site. I think you're right that the N2 is s second generation Nikon module. It has an FG setting which works for the Nikon FG and FE2 and a couple of others. I think the FG was the first (or one of the first) to use TTL flash metering.
According to the manual, switching it to FG should make it work in TTL mode - but strangely, the other end of the switch is marked for manual/TTL which should also work.
i.e. if it has a flash attached which can give the stop signal to the flash, it will work in TTL mode whereas if this signal is not received (not sent) it will fire at full power. The other settings are controlled by the on board sensor.