参考PAG clause 2.10.2-3 Working voltages in TNV circuits
9 \! R+ d8 j! B3 AIf the equipment generates a ringing signal and the circuit connects to a Telecommunication. D- k, l$ t4 u& Q/ Q
Network, the working voltage should be measured in accordance with sub-clause 2.10.4 and
3 E; O+ X) k8 |% j6 A2 LAnnex M.3.1 to determine maximum peak, rms and/or dc values.8 a8 R2 C. e! ^9 l6 D
If the equipment is intended for connection to a U.S./Canadian Telecommunication Network and
" { H' d. S, A+ c; ^receives incoming analog telecommunication signals (e.g., from a Central Office), the following6 K$ e3 q0 \ g: {/ T4 M
maximum working voltages (TNV-3) should be assumed for purposes of determining required" Z4 y- z; R/ h& z
clearances, creepage distances and electric strength test values:
: g# V# S5 o. va. peak: 200 V
0 U5 e4 E& @# i& ]& Xb. rms: 120 V
: f5 S& O7 `( t: Xc. d.c.: 60 V; k+ K* _2 f4 G" `
176 PAG 60950-1 JULY 15, 2008& d& r+ P$ q: A+ M; J
If the equipment is intended for connection to a European Telecommunication Network, consult
6 D, f7 E$ ^5 h. {9 E9 ?with IEC TR 62102, Technical Report on Electrical Safety Classification of interfaces for# }) |/ D x2 P: Q. v& \
equipment to be connected to information and communications technology networks.; I& e6 t1 ^' a! P6 W
The peak and rms values are used for clearance and electric strength determinations, and the! ~' [( k) v; V! g$ X# \8 s( g% r/ C
d.c. value is used for creepage distance." I( x6 h6 ~* n3 ^
RATIONALE:
, ]7 q5 A* S9 c" J& ]3 \; qAnnex M (normative) describes maximum voltage levels associated with Telecommunication
" q: M, n8 q$ Y9 `0 ^Signals that comply with FCC Part 68. The maximum peak value specified is 200 V referenced
! u; t% g* D) _: @5 Gto earth. Since working voltages typically are measured to earth, this value should be considered {' C6 w( o: {' M( ?% a
the maximum peak value in the U.S. and Canada.. R2 j4 ~, S4 o
Although Annex M does not contain a corresponding rms value, 120 V rms is an approximation
$ m- L, M B: s2 Oof a composite 56.5 V dc and 300 Vp-p signal. Sub-clause 2.3.5 uses 120 V rms to simulate, p7 q3 `+ ^ r F R1 W
externally generated operating voltages. Therefore this value should be used for investigation to
- ]. _: |( _8 W5 e) y& Mthis Standard. Also, sub-clause 2.10.4 indicates that cadenced ringing signals in TNV circuits) z8 J2 d, p! ]5 E# j7 h* `5 D3 K
shall not be taken into account for determining creepage distances, thus a 60 Vd.c. value may
% |% S/ c8 e7 k! Dbe used.* B; g' }( M. v: R, s
根据class III equipment定义的条款
) U) Z5 _' \+ f# M& H1.2.4.3 CLASS III EQUIPMENT: equipment in which protection against electric shock relies upon T- X0 W4 [7 D7 {
supply from SELV CIRCUITS and in which HAZARDOUS VOLTAGES are not generated' @) }' |% |9 j* N9 T
NOTE For CLASS III EQUIPMENT, although there is no requirement for protection against electric shock, all other requirements of the standard apply.) _5 X O$ G. M/ ]0 ?$ y6 y- h
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。
6 B. x2 F0 s- D$ h+ C欢迎拍砖' S% y3 U& v% g- m8 @
5 z# G* {8 x& m( x! n1 b  [s:90] |
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发表于 2011-5-12 12:06
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