Over the years I've come across those who were not aware of some of these functions of the Pfaff 1475. They may be available on other models, but the 1475 is the one with which I am acquainted. There are still a lot of this model in use.
When using the single needle foot and/or plate, there is a chance that the operator will forget and tap in a stitch which has width. This is not good for the machine and could cause the timing to be off. There is also the possibility that the needle could break and hit the operator in the eye. Ouch.
There is a security measure: touch the twin-needle button, (#29) which is lit showing it has been engaged. It will prevent any stitch from sewing which is not a straight stitch.
The presser bar lifter has several positions: up (foot lifted), down (foot engaged) and darning. In the photos, shown are up and darning.
When darning position comes in handy is when threading and using the threader. It doesn't always catch the thread the first time and the thread keeps pulling off the spool.
Putting the presser foot in the darning (part-way) position tightens the tension disks so the thread won't unwind. Be certain to do this only after the upper threading and lift it to the upper position for pulling up the bobbin thread.
To put it in this position it needs to be pushed toward the back. If you're having a problem finding the position, check it from the back of the machine.
Then there is one more position for the presser bar lifter, which is temporary and must be held up.
When having a problem getting a hoop under the bar, lift this lever just a bit higher than the up position and the hoop should fit.
This extra lift can also be used for extra thick materials and for darning.
When I first obtained this machine 23 years ago I spent a lot of time playing with it and learning what it could do. After many weeks of this, my hubby asked me if I was ever going to sew anything. Good question.