Editing Rotary dial (section)

===Recoil spring===
[[File:Rotary Dial, Dialing Back with LEDs.ogv|thumb|The back of a rotary dial in operation, with [[LED]]s attached making the contacts' states visible]]

Early dials worked by direct or forward rotating action. The pulses were generated as the dial turned toward the finger stop position.  When the user's hand motion was erratic, it could produce the wrong digit. In the late 19th century, the dial was refined to operate automatically by a recoil spring. The user selected the digit to be dialed, rotated the dial to the finger stop, then released it. The spring caused the dial to rotate back to its home position during which time constant speed was maintained with a [[centrifugal governor]].

Dials at user stations typically produced pulses at the rate of ten pulses per second (PPS), while dials on operator consoles on crossbar or electronic exchanges often pulsed at 18 PPS.

The rotary dial governor is subject to wear and aging, and may require periodic cleaning, lubrication and adjustment by a technician. In the video, the green LED shows the dial impulse pulses and the red LED shows the dial's off-normal contact function.

Off-normal contacts typically serve two additional functions. They may implement a shunt across the transmitter circuit and induction coil to maximize the pulsing signal of the dial by eliminating all internal impedances of the telephone set. Another function is to short-circuit or interrupt the telephone receiver during dialing, to prevent audible clicking noise from being heard by the telephone user.