These are the accesoires that are either required with an instrument or extentds its basic capabilities. Amongst these accesoires are tripods, staffs, prisms, levels and compasses.
Tripods come in shapes and sizes. They are used for mounting the instrument, a target or a prism. The staff is used mainly for levelling.
A prism is used together with an EDM for accurate range measurements. The targets are used together with a theodolite for aiming the instrument towards a point on the ground over which the target is placed (usually with plumb).
In this category you will find such accesoires as are mounted on the instrument themselves. Items such as compasses, levels etc.