| 摘要 |
Electrical equipment, such as telephone station apparatus, exposed to occasional, destructively high, voltage surges (e.g., lightning strikes), is protected by a device placed in parallel with the equipment, including two metal electrodes and an insulating housing. The electrodes define a fixed narrow spark gap which breaks down (arcs over) to short the voltage surge to ground. The width of the spark gap is critical, since it determines the protective breakdown voltage. In the disclosed devices the gap is closely defined although tolerances on the piece parts from which the device is made may be loose. At least one electrode consists of a flanged support member soldered to an electrode cap. The piece parts are assembled with the electrode faces in contact and raised to the soldering temperature. The gap forms as the temperature is reduced from the liquidus temperature of the soldering alloy to ambient temperature because of differential contraction between the insulator material and the metal parts. |
