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Page 300 of 504 Digital telephones line engineering
553-3001-367 Standard 3.00 August 2005
2 Add the total of all cable sections. If the total of all sections exceeds
175 ohm, select another loop.
Note: The loop resistance limit of 175 ohm must be reduced by 1 ohm for
each percent of the loop that is aerial cable (see Table 41 on page 300).
Performing Loop Diagnostic Tests
The following equipment is required for the loop diagnostic tests in
Procedure 47 on page 300:
• one volt-ohmmeter (VOM) for each test
• one 77 cable analyzer or equivalent for each test
Procedure 47
Testing foreign voltage
1 Set the VOM range switch to a scale 60 V DC/V AC or greater.
2 Connect the VOM test probes to the loop at the line card or distributing
frame.
3 Measure the DC and AC voltage between the following points under
no-load conditions:
• tip (T) and ring (R)
• T and ground (GND)
• R and GND
Requirement: Voltage readings should be less than 1 V DC/V AC.
Table 41
Conductor resistance per unit
Gauge Ohm per loop kft Ohm per loop km
26 83 278
24 52 173
22 33 109
19 16 54