3. SubclassesThe following table lists the features of the various subclasses.Subclass Material Double- Hook Thread Edge EdgerNeedle Left Trimmer CutterLegend: M = medium-heavy material / x = standard / - = not available3.1 Optional equipmentThe following optional equipment can be supplied for the 767:RAP 13-2 *) Electro-pneumatic stitch locking and sewing-foot lift, pedal-operated.RAP 13-4 Electro-pneumatic stitch locking and sewing-foot lift, pedal-operated.RAP 13-6 **) Electro-pneumatic stitch locking and sewing-foot lift, pedal-operated.RAP 13-6 ****) Electro-pneumatic stitch locking and sewing-foot lift, pedal-operated.RAP 13-7 ***) Electro-pneumatic stitch locking and sewing-foot lift, pedal-operated.FLP 13-2 Electro-pneumatic sewing-foot lift, pedal-operated.NK 13-1 Pneumatic needle cooling, pedal-operated.NP 13-4 Electro-pneumatic needle-retraction device for maximum clearancebeneath sewing feet when lifted.HP 13-7****) Electro-pneumatic rapid stroke adjustment by knee switch.SP 470 Roller feed device, with adjustable upper and lower conveyor rollers.WTA 13-2 Automatic lowering for upper conveyor roller.LR 13-4 Light barrier for automatic triggering of RAP at end of thread.KNS 2 Knee switch for triggering manual reverse sewing.WE 3 Maintenance unit.WE 6 Maintenance unit for pneumatic optional equipment.RFW 13-3 Residual-thread monitor bobbin thread.RFW 13-8 Residual-thread monitor bobbin thread (KFA).RFW 13-9 Residual-thread monitor bobbin thread (oversized hook).STLS 13-2 2nd Stitch length.FS 13-1 Additional tension.N800 005611 Seam center guide.*) **) ***) ****) = Integrated for the subclasses6- 73 M - - - - -- AE - 73 M - x - x x- AE - 5 - 73 M - x - x x- FA - 73 M - - x - -- LG - 73 M - x - - x- FA - 273 M x - x - -- FA S - 473 ***) M x - x - -- 373 M - - - - -- FA - 373 *) M - - x - -- KFA - 373 **) M - - x - -- KFA - 573 ****) M - - x - -- FAS - 373 ***) M - - x - -- FAS - 573 ***) M - - x - -- VF - 373 M - x x x -- VF - 573 M - x x x -