[GreenKeys] Model 28 signal lines

[Jim Haynes]

On Wed, 16 Oct 2019, Paul Heller wrote:
> Barry,
> My only point, and others may disagree, is that 48v is not enough. 

Oh, I was going to say that too.  Although with perfect signals like
you get off itty it might be OK.  Also there was a constant-current
circuit in QST a long time ago and I believe the article said it was
good to use with 48V.  I keep wishing someone who knows how would
simulate that circuit and see what kind of rise and fall times can
be achieved versus the simple power supply and resistor loop.