| 摘要 |
<p>An overvoltage protection device, for protecting communications equipment against hazardous voltages due to lightning or power surges, comprises a primary protector (10), for example a gas tube device, and a back-up protector (16) connected in parallel. The back-up protector includes a semiconductor pn junction, and is preferably a pair of diodes (18, 20) back-to-back. The back-up protector has a breakdown voltage slightly higher than that of the primary protector and is arranged to fail short-circuit once it has operated so as to provide an indication that the primary protector failed to operate.</p> |
