[GreenKeys] Model 28ASR loop

[The Rices]

Question for anyone familiar with the Model 28ASR. I have looked through the 
schematics I have found on line and see that the loop normally goes in on 
terminals 1 and 2 of the terminal strip. In this configuration is the loop 
power normally supplied externally? I have looked at a way to use the 
internal power supply to generate loop and using it in test mode can hook up 
the terminal unit that way but was trying to see if there was a way that by 
moving some jumpers I could get the loop power in the line mode. The images 
I have of the schematics are kind of hard to read I see as well so that may 
be part of my ability to trace it completely.

I can supply external loop power from the terminal unit but it is at 60 ma 
and not sure what to check to be sure that is fine as I see in test mode the 
local loop current is 20ma.

Thanks in advance for any ideas to check.

Steve
N4YZA