Modern doorbells often incorporate intercoms and miniature video cameras to increase security. Some old doorbells, for example, the Soviet ZM-1U4, use mercury switches as current interrupters. There are old doorbells, a dumbwaiter and a dial-up telephone. By the early 1900s, electric doorbells had become commonplace. As with wireless doorbells, musical doorbells have also become more common. They will then start to ring the doorbells of households. "Looky Looky Yonder" and "Yellow Woman's Doorbells". Wise recalled thinking that his first NES projects sounded like doorbells. Alarming concerns regarding the security of the smart doorbells have been raised. The Messaging specification defines Doorbells and Messages. Other examples of them are doorbells.