| 摘要 |
A coaxial drop cable safety device is used for cable television, data a nd telephony applications. The device is used on buried drop cable where 60 Hz powering voltages applied to the drop cable exceed low voltage safety limits and where the drop cable is buried at depths which is less than the minimum required to meet electrical safety codes. Tap end and premise end units are connected to the drop cable. The tap end unit applies a DC voltage to the centre conductor of the drop cable. A monitoring circuit in the tap end unit monitors the DC current in t he centre conductor. The tap unit will immediately remove the powering voltage In the event of either an open or faulted condition on the centre conductor along the entire length of the drop cable. Additionally, while providing fault protection for the low frequency powering circuit due to tampering or damage to the cable, the fault monitori ng circuit allows the high frequency television, data and telephony signals to pass wit h little or no impediment.
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