参考PAG clause 2.10.2-3 Working voltages in TNV circuits
: z' u2 W9 M2 NIf the equipment generates a ringing signal and the circuit connects to a Telecommunication
, C4 _, v. {; j/ @% vNetwork, the working voltage should be measured in accordance with sub-clause 2.10.4 and3 \ s/ p4 J. v5 L" ?
Annex M.3.1 to determine maximum peak, rms and/or dc values., l" ]( [, _) l$ F! [
If the equipment is intended for connection to a U.S./Canadian Telecommunication Network and6 L. D8 R. c) w& c( P) G
receives incoming analog telecommunication signals (e.g., from a Central Office), the following" S; \) @# a9 B, ^* j9 n" p
maximum working voltages (TNV-3) should be assumed for purposes of determining required) X% W B- D( z" W! s" w
clearances, creepage distances and electric strength test values:
& ?% ~$ \7 e" [; ]7 ba. peak: 200 V
/ U" Z! L# _% G1 M1 f' Ib. rms: 120 V
2 `7 I7 b7 @. T1 Qc. d.c.: 60 V
( Y5 u1 ?0 a& ~' ]3 ]$ Y3 w% l$ @" {176 PAG 60950-1 JULY 15, 2008
, e% u4 R/ v9 C3 r& a7 v3 q. vIf the equipment is intended for connection to a European Telecommunication Network, consult
/ ?9 b4 C; G3 Ywith IEC TR 62102, Technical Report on Electrical Safety Classification of interfaces for
9 s! J$ T1 B- ]& w/ s: Y' Cequipment to be connected to information and communications technology networks.- Z8 i. V8 ?, |( O
The peak and rms values are used for clearance and electric strength determinations, and the
& [+ h' n, o9 w0 dd.c. value is used for creepage distance.% E# G2 j+ ~. }. L
RATIONALE:. @6 b; G2 F# k) R
Annex M (normative) describes maximum voltage levels associated with Telecommunication- [& l8 B. a& B1 ^; p, C( p
Signals that comply with FCC Part 68. The maximum peak value specified is 200 V referenced6 G' ^! r8 V" Y0 M5 {
to earth. Since working voltages typically are measured to earth, this value should be considered
! f, w" v E5 e+ D. E- B- p& T3 ]the maximum peak value in the U.S. and Canada.; p# |. b# I+ b3 a; c( V- j( _
Although Annex M does not contain a corresponding rms value, 120 V rms is an approximation
9 i6 Z1 ]8 y/ L% Z& ^. Gof a composite 56.5 V dc and 300 Vp-p signal. Sub-clause 2.3.5 uses 120 V rms to simulate$ ^+ q4 k5 `+ P8 ?
externally generated operating voltages. Therefore this value should be used for investigation to; U% |8 K0 a% P8 E2 R6 H! F
this Standard. Also, sub-clause 2.10.4 indicates that cadenced ringing signals in TNV circuits& t) Z. d2 l+ R6 x# |8 j
shall not be taken into account for determining creepage distances, thus a 60 Vd.c. value may
9 I& a$ }# n# s; j- N" Cbe used. \: ?, r7 A! @8 q6 f! H
根据class III equipment定义的条款
5 y7 j7 ?: `4 q. C D1.2.4.3 CLASS III EQUIPMENT: equipment in which protection against electric shock relies upon
9 n) D) t' z% W/ L. O, G0 e' ^5 ssupply from SELV CIRCUITS and in which HAZARDOUS VOLTAGES are not generated
$ s: r. d9 ~" E9 k/ d) s- F6 FNOTE For CLASS III EQUIPMENT, although there is no requirement for protection against electric shock, all other requirements of the standard apply.$ r' c* }7 s' a0 v
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。! {( y! ?( L/ f z. b+ K$ M
欢迎拍砖
" l) M, V. \' S& U/ U7 M. j# X
9 V, O: j" a- s+ n$ r; w3 t4 ]  [s:90] |
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发表于 2011-5-12 12:06
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