| 摘要 |
A control system for a reversible electric motor 10 which drives a roller shutter door 13 between upper and lower limiting positions, has a reversing switch 11 and limit switches 25, 26 respectively operable by a part 27 on the door 13 in its upper and lower positions to cause the switch 11 to arrest door movement. A timer switch 28, 31, is operated by the switch 25 and causes the door 13 to be lowered after a predetermined interval in its upper position. Raising of the door may be caused by a sensing device 20 responsive to the presence of a vehicle. If an obstruction is detected by detector 30 while the door is being lowered, the door moves upwards and remains in its upper position. <IMAGE> |
