| 摘要 |
<p>Secondary surge protection means for equipment connected to transmission lines, for example line-powered amplifiers (10) interconnecting T1 or T1C telephone lines, includes two diode bridges (21; 26) and a pair of surge diverters (30; 31). One diode bridge has its cathode/anode nodes connected one to each conductor (11; 12) of an incoming transmission line. The other diode bridge is connected in like manner to an outgoing transmission line (13; 14). Each surge diverter interconnects the anode/anode node (23) of one bridge and the cathode/cathode node (32) of the other bridge. When a surge on one line causes the voltage across one or other diverter to exceed a predetermined threshold, the diverter conducts, shunting the surge past the amplifier to dissipate in the other line. The two transmission lines may be coupled to the input and output, respectively, of one amplifier, or to the input of one amplifier and the output of a different, oppositely connected amplifier. In both cases, power for the or each amplifier may be derived from the two lines, for example by a Zener diode (35) interconnecting them in known manner. The characteristics of each surge diverter are such that it will respond to fast rise-time lightning pulses yet tolerate long duration power surges, and will be operated by differential mode or common mode surges.</p> |
