1. Field of the Invention
The present invention relates to a rotary encoder, which is applied to a frequency selecting dial part of a digital tuner, a part for measuring the amount of movement of a mouse or the like.
2. Description of the Background Art
FIG. 1 illustrates the structure of a conventional contact type rotary encoder, which is applied to a frequency selecting dial part of a digital tuner, for example.
When a frequency selecting dial I is rotated, a rotary plate 3 coupled to the dial I through a rotary shaft 2 is rotated in the same direction as the dial 1, whereby a contact part 5 fixed by a holder 4 is repeatedly brought into contact with / separated from electrodes 6, which are provided on the rotary plate 3. Pulses are generated by such repetition of contact/separation between the contact part 5 and the electrodes 6, to change a frequency selected by the tuner in response to the number of the generated pulses.
In the conventional rotary encoder having the aforementioned structure the electrodes 6 are arranged on the rotary plate 3 as shown in FIG. 2. Therefore, the number of pulses generated every rotation of the rotary plate 3 is fixed sO that the rotary plate 3 must be replaced in order to mechanically change the ratio of &he angle of rotation of the rotary plate 3 tO the number of generated pulses.