Today, I put two 10 mA TD's on my 576 CT. I set it at 15 V max, 650 Ohm series resistor (lowest setting of 576).
Nothing special, NPN polarity, internal Step Generator off. TD between "C" and "E".
Nice curves (see two "TD 10 mA" images), see two added images. I don't understand why you (Albert and Dennis), are surprised by the clarity of the curves (Eric's and mine). Maybe you used a 577 and the 576 is an exception.
TD 10 mA - 2 fell ill while on the CT and hasn't recovered. See text accompanying image in album.
Apologies for the lesser quality photographs. There was a lot of light behind me that I was trying to screen with my body.
Raymond
Raymond Domp Frank