I tried this circuit just today, and remember pin 8
needs GND (not in schematic). I couldn't get the control
voltage range indicated to keep my servo from far CCW
(I couldn't get it to move beyond "10 o'clock" at all). I
even tried the V all the way up to my supply (regulated
5v, so maybe that's why?). I altered the monostable's
capacitor, to no ideal, until I changed R4 to less resistance,
but I still couldn't get beyond "2 o'clock". It also made
"bottom out" noise at full CCW. All of this via diodes for
cutting the voltage down & testing 5V all the way to 2.6V.
BTW, I did get it to work however, by leaving in 3 diodes
in series to pin 5 of the monostable, and using a 4.7K
resistor in series with a 20K potentioneter for R4. In case
this is of any use and would like to control the servo by
resistance instead of V.