| 摘要 |
<p>A counter comprises a series of hollow digit-displaying drums (13-17), with mechanical driving connections (18 - 21) driving succeeding drums so that a decimal total number is set up. The higher significance digit drums (14 - 17) each carry an optical encoder comprising a cylindrical surface with slots forming a binary code which is related to the displayed digit. U-section reading devices (30 - 33) straddle the encoder to read the code and produce an electrical coded output. To avoid problems caused by readings at changeover points, the lowest significance digit-displaying drum (13) is associated with an impulse drive which is triggered at each changeover point to drive the drum forward so that it does not come to rest at the changeover point. The impulse drive comprises an off-centre weight which rotates with the drum.</p> |
