The range of instruments can be differentiated through various criteria. The construction of the instrument is important. Electrically analogous instruments are simple instruments. The emitted electricity is logically subject to variations. The electrical safeguard of the machine is not necessarily bad, but is limited because of its construction.
Modern instruments have a digital system.
This has the advantage of allowing the electricity to flow evenly as it has been programmed by the user. The electronics control the emitted electricity and correct it constantly, if necessary. An important difference between the various instruments are the number of outgoing channels. Two needles can be attached per channel, e.g. with five channels, five pairs of needles can be attached. The more channels an instrument has, the more acupuncture points can be stimulated simultaneously.