Common shift switch band switch and a multimeter rotary switch, whose structure there are two:

One is the BBM (Break Before Make) contact, which is about the change when contacts first before disconnecting after contact connected contacts, there is a before and after contact is broken:

The other is MBB (Make Before Break) contact, which is about the change when contacts are contacts with contacts before and after States. then disconnect the front contact, maintain contact with the Bottom contact. According to circuit in circuit design uses to choose the right rotary switch and circuit safety.