This not compatible with UHU controller. This improvement servodrive Elm Chan http://elm-chan.org/works/smc/report_e.html. Discussing the improvement goes in russian forum http://forum.rcdesign.ru/index.php?showtopic=40981.
Apropos on scheme there is errors ( HL1,H2 - LED, Anode VD16, VD19 to Gnd). The New variant of the scheme with checking the current and external amplifier photointerrupter here.
Excuse me for my bad English.