Each subscriber’s telephone instrument is fitted with a dial which turns round on a pivot at its centre. This dial has a series of holes round its circumference, numbered consecutively from 1 to 9, and 0. Suppose now a subscriber wishes to speak to a friend whose telephone number is 2583. He removes the receiver from its hook, places his finger in the hole marked 2, and turns the dial round in a clockwise direction until his finger comes in contact with a stop. He then removes his finger, and the dial automatically returns to its original position. He then places his finger in the hole marked 5, and again turns the dial as far as the stop, and when the dial has returned to the normal position he repeats the process with his finger placed successively in the holes marked 8 and 3. He now places the receiver to his ear, and by the time he has done this the automatic mechanism at the exchange has made the necessary connexions, and has rung the bell of subscriber number 2583. On completing the conversation each subscriber returns his receiver to its hook, and the exchange mechanism returns to its normal position. The turning of the dial by the finger coils up a spring, and this spring, acting along with a speed governor, makes the dial return to its first position at a certain definite speed as soon as the finger is removed. During this retrograde movement a switch automatically sends out into the line a certain number of impulses, the number being determined by the hole in which the finger is placed. In the case supposed, groups of two, five, eight, and three impulses respectively would be sent out, each group separated from the next by an interval during which the subscriber is turning the dial.