| 摘要 |
The apparatus includes an elongate narrow plate (10) as the signal emitter arranged for displacement between a detector (12) and a source of light (14) which are disposed in a facing relationship in the two vertical limbs of a U-shaped block (16). The signal emitter (10) has a number of apertures (18) through which light passes between the light sources in the limb (14) and the detectors in the limb (12). The signal forming apertures in the plate (10) are arranged in vertical groups (20) enabling the transmission of coded signal information. The spacing between adjacent vertical sets of apertures in the plate (10) relative to the size of the detector enables signal transmission at all times. |
