Ok Chetts, I have the wrong interface up without the attach option however I found it by clicking the "Go Advanced" button, here's my schematic.
The basic circuit at the top shows how simple it is
I found that some inductive loads tend to oscilate, the fix was adding a small capacitor as shown.
For batteries I use the small transistor type 9V. I tried rechargables once but they were more trouble than they were worth, a pair of batteries last over a year if you remember to turn it off or break the circuit. It can be used without a battery for Transmitter Simulate mode.
The resistor and pot in line with the regulator Out pin set the initial 4 mA (zero)
I may have drawn the zenner backwards but you get the idea it's just for testing the battery so the voltage is not important, anything from 6-12V will do.
The resistor values shown are the sum of fixed plus trim pot, these are calculated values based on 1.25V from Adj to Out, best to set each pot with a good mA meter. I made my calibrator over 25 years ago and never had to adjust the pots, I check occasionally against my Fluke 87