This is a voltage-controlled stereo signal attenuator. A 30-volt DC control voltage (the 300-ohm pot functions as a lamp-dimmer) energizes a lamp (I'm guessing the General Electric #313 is an ordinary miniature incandescent bulb) which radiates light energy onto the two "LOR 1-C" components. These are variable resistors (some sort of photocell) which are in the signal path of each of the two channels. SO the single D.C. control voltage affects the two audio channels simultaneously.
I dare say, this circuit probably has an operating range not in excess of 40db of attenuation. It may also exhibit significant non-linearity across the entire audio spectrum, which probably delighted Mr. Tudor!
-Bob (R. Albert Falesch )
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