参考PAG clause 2.10.2-3 Working voltages in TNV circuits, D4 L. A7 \- n0 M9 U/ N& s
If the equipment generates a ringing signal and the circuit connects to a Telecommunication
5 t* B# }# H. j uNetwork, the working voltage should be measured in accordance with sub-clause 2.10.4 and
8 `# @9 S3 J$ a+ k1 R$ |) HAnnex M.3.1 to determine maximum peak, rms and/or dc values.
. n9 F. D7 m: E: G) M4 ]- d/ BIf the equipment is intended for connection to a U.S./Canadian Telecommunication Network and
/ ~" @ h Z5 z: \/ N4 Areceives incoming analog telecommunication signals (e.g., from a Central Office), the following: ^- N8 v3 \0 S" h+ ]& O% g
maximum working voltages (TNV-3) should be assumed for purposes of determining required
4 }8 d) L* ~* ^4 r! T8 b3 t; `clearances, creepage distances and electric strength test values:; Y# u e( e; N- V! ?
a. peak: 200 V
0 q! P" T2 e. s* e$ yb. rms: 120 V0 p% Y! ]6 i) @6 I, m3 m( S
c. d.c.: 60 V
- @/ a! H' T+ D176 PAG 60950-1 JULY 15, 2008! g9 x- A9 u+ B7 ?% `
If the equipment is intended for connection to a European Telecommunication Network, consult/ R6 P. R- E- j% F7 `* g
with IEC TR 62102, Technical Report on Electrical Safety Classification of interfaces for6 E' k! g+ t2 J
equipment to be connected to information and communications technology networks.( F; x K! H9 j: |1 ]8 T3 u. C
The peak and rms values are used for clearance and electric strength determinations, and the
5 E2 S0 p( |- v. H. e. ]d.c. value is used for creepage distance.( s/ X- H1 I* Q8 V
RATIONALE:- Z) P c, E6 h' l% S8 E
Annex M (normative) describes maximum voltage levels associated with Telecommunication
, M- G( T, A5 } R4 t& fSignals that comply with FCC Part 68. The maximum peak value specified is 200 V referenced% D, S$ }1 A# S1 c$ G
to earth. Since working voltages typically are measured to earth, this value should be considered& y, f( ]3 U( K% A ]
the maximum peak value in the U.S. and Canada.' c5 T1 n i- M0 d
Although Annex M does not contain a corresponding rms value, 120 V rms is an approximation
) K# i0 B" {3 t. m* Aof a composite 56.5 V dc and 300 Vp-p signal. Sub-clause 2.3.5 uses 120 V rms to simulate& d. |2 r% E! G" [6 T, O, G
externally generated operating voltages. Therefore this value should be used for investigation to7 t, @- S8 ?2 w
this Standard. Also, sub-clause 2.10.4 indicates that cadenced ringing signals in TNV circuits
# Z3 r6 S; D7 n! A; J, z9 x' B- |shall not be taken into account for determining creepage distances, thus a 60 Vd.c. value may
4 c# B' b& ^8 H9 }" J+ u K* \' }be used.: @1 N3 I l( d( L# g* x) Z2 p
根据class III equipment定义的条款) G" o, H1 R+ M
1.2.4.3 CLASS III EQUIPMENT: equipment in which protection against electric shock relies upon
2 [2 v6 b1 f% j# _* esupply from SELV CIRCUITS and in which HAZARDOUS VOLTAGES are not generated
+ s3 \8 h# z0 O" c: b5 r: U7 [NOTE For CLASS III EQUIPMENT, although there is no requirement for protection against electric shock, all other requirements of the standard apply.
# u% V4 {1 U* e我认为应属TNV-3的设备也应属CLASS III，因为其只是接受来自上游的Ring singal，不是自己内部产生。
$ o0 A, V7 c8 o( |3 Z欢迎拍砖; j7 J% S0 H+ _, U
T7 F8 S. C# e5 N  [s:90] |
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