Cortelco network simplication of WE?

[Alex G. Bell]

I,m sorry, I do not have a suitable powersupply.  The way tha voltage of the diodes was determined was just by using a laptop power in series with a 1k Resistor, and measuring the voltage across the diode. 

As you see this network is even simpler than the 4293 someone mentioned.  The picture show a PCB with room for several other components.

dsk

You could accomplish useful measurements with a fixed voltage and variable resistance.  You need to vary the current through the diodes and measure the voltage across them.  You could simply add a variable resistance in series with a phone line as the current source, varying the loop current from 20-100mA.