| 摘要 |
This intention relates to a constant attendance system for use in the control of machinery. The invention provides a system which is necessary to operate a constant attendance switch 4 at regular time intervals. The switch must be operated when a signal such as a light 6 is active. If the switch is not operated and released the machinery is caused to stop by the action of timing devices TR2, TR3 whose actions are controlled by the switch. The system operation is initiated by actuation of a dead man handle 3 and with the switch 4 in a first position, a first timer TR1 is activated to close a relay contact 5 after a delay to activate a second timer TR2 and a lamp or an audible device 6. The switch 4 is then depressed to reset the timers TR1, TR2 and to extinguish the lamp. The switch 4 is alternately depressed and released before the respective timing period of TR2, TR3 to prevent system shutdown by respective relays 7, 8. <IMAGE> |
