707 friends

I have the following question for a long time.

After starting the 707 and having disconnected external power and air
Essential power source selector and AC paralleling selector is set on GEN 3..... but what has one to do with :
1/. The load & volt selector ? Keep it on ESS TR or also on GEN 3 ?
2/. What to do with the battery switch ? Keep it on ON or OFF ?
    If I put the switch on off, all power on the instruments is lost. Is this correct ? Does the 707 always operates with batteries on for the whole flight ?
:-?

Thank you very much for your consideration.

Jan Koppen
Amsterdam - Netherlands :)