Charley:
The OBEL switch switches the effects loop in and out of the signal chain. When the OBEL is switched on, and there is nothing plugged into the OBEL stereo jack, you should get little, if any, signal getting through. If you're running the guitar out to the effects, then to the amp, you're not using the OBEL. In this situation, one position of the OBEL switch should give you full signal, the other little or no signal. If you are getting full signal in one of the positions, then your battery has some juice in it. If the pre-amp battery is dead, you shouldn't get any signal. As for up vs. down, I'm not sure off the top of my head, but if I can get to my instruments later today, I'll check.
Bill, tgo