m 23x10-3

3.5.3. Loop Length

The method of determining subscriber loop length using the signal resistance limit as a basis is called the basic resistance design. The maximum subscriber loop length, which is defined as the distance from the subscriber to the central office, is expressed as

Loop resistance limit RL

dc loop resistance Rdc The dc loop resistance is measured in ohms per kilometer and expressed as

Where 'd' is the diameter of the conductor in millimeters.

Example 3.3. Calculate dc loop resistance, if the loop resistance limit is 1250 ohm for the loop length of 10 km.

Rdc L 10 km

3.5.4. Cable size for the Loop

From the equation 3.13 with the knowledge of dc loop resistance, the diameter of copper wire can be determined. The table shows American Wire Gauge (AWG) versus wire diameter and resistance. From the table 3.4, for the required diameter of the cable, the size of wire gauge can be determined.

Table 3.4. AWG versus wire diameter and resistance


diameter 'd' (mm)

Rdc (Q/kM)

Attenuation or loss per km (dB/km)

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