FCC PART 68 测试标准
电话机、PTSN等电信设备标准ANSI/TIA-968-B-标准
ANSI/TIA-968-A-标准
Table 6 – Simulated ringing voltages and impedance limitations
Ringing type Range of compatible ringing frequencies (Hz)Simulated ringing voltage superimposed on 56.5 VDC Impedance limitation (ohms)
A 20 ± 3 40 to 130 V rms 1400
A 30 ± 3 40 to 130 V rms 1000
B 15.3 to 34 40 to 130 V rms 1600
B >34 to 4 62 to 130 V rms 1600
B >49 to 6 62 to 150 V rms 1600
NOTE – Specifications for Type B ringing are no longer part of this standard
5.1.11.2.3 DC current during ringing: During the application of simulated ringing, as listed in table 6, to a loop start interface, the total DC current shall not exceed 3.0 mA.
5.1.11.2.4 Ringing frequency impedance (metallic): During the application of simulated ringing, as listed in table 6 to a loop start interface, the impedance between the tip and ring conductors (defined as the quotient of applied AC voltage divided by resulting true rms current) shall be greater than or equal to the value specified in table 6.
5.1.11.2.6 Ringer equivalence definition: The ringer equivalence number shall be the value determined in 5.1.11.2.7, followed by the ringer type letter “A” indicating the frequencies for which the number is valid. Testing shall be performed at each frequency specified for Type A ringing, and the largest ringer equivalence number so determined shall be associated with that ringing type. Requirements for Type B ringing are no longer specified in this standard.
5.1.11.2.7 Ringer equivalence for equipment operating on loop start telephone facilities: The ringer equivalence shall be five times the impedance limitation listed in table 6, divided by the minimum measured AC impedance, as defined in 5.1.11.2.4, during the application of simulated ringing as listed in table 6.
5.1.11.2.8 Maximum ringer equivalence: All approved terminal equipment and approved protective circuitry that can affect the ringing frequency impedance shall be assigned a ringer equivalence. The sum of all such ringer equivalences on a given telephone line or loop shall not exceed 5. In some cases, a system that has a total ringer equivalence of 5 or more may not be usable on a given telephone line or loop.
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