APPENDIX
Appendix 1
Appendix
Generally Accepted Criteria for Plain Old
Telephone Service
Parameter Acceptable Marginal Unacceptable
Loop Current mA ≥23
2
≥20< 23
2
<20
1,
2
Circuit loss dBm ≤8.5 – >8.5
Metallic Noise dBrnC
≤20 >20< 30 ≥30
Power Influence dBrnC
≤80 >80<90 ≥90
Balance dB
≥60 >50<63 ≤50
*Station Ground Ohms
≤25 ––– > 25
Slope dB
≤7.5 ––– > 7.5
Parameter Insulation Light Fault Heavy
Good (Service Fault
Affected)
3
(Out of
Service)
Insulation
Resistance
≥ 3.3 MOhms >2.8 kOhms ≤2800 Ohms
< 3.3 MOhms
1
These are negative values.
2
>18 to <20 mA acceptable for emergency service only.
3
Lines having good insulation but equipped with ringer
isolators or selective ringing devices will test as having light
faults on tip and ring.
NOTE: > means “more than”
≥ means “more than or equal to”
< means “less than”
≤ means “less than or equal to”
* On some floatingĆtip switches, such as #5 ESS, ground
resistance cannot be measured because the switch
operates on a floating ground.
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