[old_tv_nut]

When I look up the 1077, it says it's a sweep comparator.

I may not have it exactly right, but I think the idea is to test an RF amplifier or other device by connecting it to the "Unit Under Test" terminals and then look at the demodulator out signal with a scope locked to the sweep generator (which should be attached to the RF IN). Then (presuming the comparator has an internal circuit that switches back and forth between the Unit Under Test and an internal attenuator), you would get a very accurate measure of the gain or loss of the unit under test. I believe the numbered knobs on the left attenuate the signal to the unit under test and the knobs on the right attenuate the comparison signal. You would adjust the ones on the left to get a reasonable signal level for the unit under test, then adjust the ones on the right to get equal output from the unit under test and the comparison signal, and the difference between the left and right settings then is an accurate measure of gain or loss of the unit under test.