| 摘要 |
<p>The time delay switch, for emergency telephone call systems, has switching contacts which are closed when the switch is operated and which are held closed for a limited time after closure. At the rear are the terminals, and underneath is a swinging arms which after operation is held down by a spring (12) at one side. This is operated by a toothed switching wheel (16) and a sto wheel (17) and a ratchet arm (25). These form a dead centre mechanism, combined with a second spring n26) anchored at one end to the frame f the switch and secured at the other end to the ratchet arm. This controls the return action, the teeth of the wheels having different formations (21, 22, 23).</p> |
