Panoramic TTG-1 two-tone generator -need the book or help?

Hard to believe it was October 2012 when I got this and just now got around to it.

Panoramic TTG-1 two-tone audio generator. One tone can be selected for 0.7, 1.1, 1.5, or 1.9 KC, The other has 4 freq's 200-600Hz higher up to 2.5KC.

(not the same as the TMC TTG-1)

I cleaned it up and got it working, but there are two level controls on the back, and they affect the regulated or leveled output of the unit. The circuit for either oscillator has its frequency determined by some precision resistors and capacitors, selected by its front-panel switch.

The way the output voltage is regulated is to include a 3W 120V lamp in the oscillator feedback circuit. The lamp is part of the load as well, and is used with a large resistor and the aforementioned output controls. It works so that as the signal voltage goes up, the lamp gets hotter and its resistance goes up, reducing the feedback or gain of the loop and bringing the output to a constant value.

The problem, which is not really a show stopper, is that when the frequency is changed, the circuit voltage has to be stabilized by the thermal characteristics of the lamp, so the result is that the amplitude level 'rings' or oscillates at 2-5Hz in a decaying manner. It takes a couple seconds for the amplitude to settle to the regulated level. The level controls on the back, one for each oscillator, affect the time taken to settle, because the level naturally affects the amount of average power going to the lamp. In normal operation, the filament, observed in darkness, just barely glows or does not glow at all. For different settings of the level controls, the 'ringing' of the level is either damped quickly or not at all. If set to dampen too quickly, the output signal can be so large that the unit's tone mixer and output amplifier can clip.

So there is a narrow range that is acceptable.

The answer to my 'problem' is how to set the level controls, that is, what is the right level to come out of the output terminals on the unit?

Therefore I am asking if anyone knows this unit, or if anyone has the book/manual freely available that I could copy.

I am already using the unit but I would prefer to 'calibrate' it. I'm hooked on using a two tone generator now. Less stress while testing into a load.