If the operator has just one belt it is probably the T 1 C. If it has three belts it is probably the TH operator which is the better of the two. The TH had a series field in the door motor. It is possible you have a dirty A or B contact which are indeed the two door limits. Everything else is slightly subjective although they did use to list the contact make break points on the straight lines area 40-49. Make sure you don't have a dirty CL 7-8 contact which is your interlocking contact. It is a common failure. The setup is similar for the T1c although it is generally regarded as a piece of crap. The common failure here is that the operator sheave wears out. One of the things we use to do was to slightly ream the 8/32 screws holding the music box so we could increase the followup on A and B contact.
