I got tired of my key contacts getting all grungy from keying 
over 50V and over 100ma. Above that level I find I have to clean
them every 2 or 3 transmissions.
Of course, my contacts are steel; not electrosuvium, so I'm 
asking for it. The tiniest of arcs seem to create carbon soot 
or some spongy feeling conduction which messes up keying.
I see that in older books this has been a problems since line 
telegraph.

In short I am using a 3 stage DC amplifier to allow keying 250ma
(tested) with only 55ua of key current.

The unusual 2nd and 3rd stage Darlington circuit allow using a
low voltage (red) transistor to key the high voltage one (Q3).

The strange key input protects Q1 (black).