| 摘要 |
<p>1276801 Protective arrangements RELIABLE ELECTRIC CO 12 Jan 1971 1373/71 Heading H2K [Also in Division H1] A line protector for a communications circuit comprises an insulating member 45 having conductive material 51 thereon disposed between an increasing terminal 25, 35 and an outgoing terminal 29, 39, Fig. 4, a spring 59 engaging the conducting material 51, and an air gap assembly 67, a contact member 72 and a fusible element 74 disposed between the spring 59 and an earth terminal 27, 37. When an overvoltage occurs, an arc is produced in the assembly 67 to complete a circuit between the incoming terminal and earth. Should this condition be prolonged, the element 74 is melted and the spring 59 moves the contact member 72 so that it bridges the earth and incoming terminals. In the event of overload, a heater 82 interconnecting the printed conducting areas 51, 55 which co-operate with the terminal 35 and the outgoing terminal 39, melts fusible material to release a ratchet wheel 92 which turns, releasing itself from a fixed pawl 98. The spring 59 is now able to move the insulating member 45 upwardly to interrupt the circuit between the incoming and outgoing terminals and to complete a circuit between the incoming terminal 35 and the earth terminal 37 through the conducting area 51. A circuit is also completed from the terminals 35, 37 to an alarm circuit terminal 31. A part 47 projects through an opening in the housing to indicate the overcurrent tripping and is used for reclosing after overcurrent tripping. The protector shown has two of the above arrangements, but with a common contact 72, fusible element 74 and earth terminal and is used to protect both lines of a communication circuit.</p> |
