How can I locate a double fault without a known-good pair?

K-Test Specifications: 
Resistance to Fault accuracy: 1% Resistance to Strap 1 Ohm.
Other Specifications: Same as RFL, with restrictions stated above.
 
K-Test Operation: 
 

1. After running the initial RFL test, pairs having a double-sided fault will be shown on a screen that offers the new K-Test option, as shown in Figure 1. 
2. Press the K-Test (2W) softkey to start the first phase of the operation, during which the 990 measures fault resistances and it performs an RFL nulling sequence with the far end open.
   
   HINWEIS: If one fault is not greater than twice the other fault, an error message will be displayed at this point, and the K-Test will terminate.
3. If the fault ratio requirement is met, the 990 will prompt you to connect a far-end T-R short. The unit may be powered down at this point, as with other RFL options, and the test resumed (Continue Prev. Test) after the short is connected.
4. With the strapping prompt screen displayed, press the TEST key. This starts the second phase of the K-Test, during which the 990 measures the Loop Resistance and performs an RFL nulling sequence with the far end shorted. 
   
   HINWEIS: If the larger fault value is less than 100 times the Loop Resistance, a message will be displayed stating that the accuracy may be reduced. 
5. The 990 will then display Resistance-to-Fault and Strap values, like the normal RFL routine. If the cable gauge and temperature (upper right corner) are correct, press the Distance to Fault (F1) softkey to view the results. If the wire gauge or temperature needs to be changed, follow normal RFL procedures to make the changes and then press Distance to Fault.
    
   
                                                 Abbildung 1: RFL Test Screen, K-Test Option (2W)
    
   Opens Test: Open Tip on a Working Pair
   This enhancement to the Opens Test allows you to measure the 2-Terminal capacitive length and capacitance on a pair having either excessive DC voltage or a severe resistance fault. It effectively provides the ability to measure the Open Tip length on a working POTS pair (having battery on the Ring leg), as well as measure the length of an unfaulted leg on a pair with a severe battery cross or ground fault. At the conclusion of an Opens Test on a working pair with an open Tip, or a severely faulted pair, press the new Contin. Opens softkey as shown in Figure 2.
    
    
   
                                     Abbildung 2: Opens Test Result, Working Pair Open Tip
    
   This figure shows the resulting screen from an Opens Test on a working POTS line having an open Tip. Pressing the Contin. Opens softkey will cause the tester to begin a continuous length measurement on the first unfaulted leg of the pair, in this case the Tip-Ground leg. If a faulted leg (either voltage or resistance) is then selected, the tester will beep, prohibiting the measurement.