参考PAG clause 2.10.2-3 Working voltages in TNV circuits
0 A0 d: O" z% D5 N, {5 K# ?If the equipment generates a ringing signal and the circuit connects to a Telecommunication5 {2 U& M3 I" j. g& G' G
Network, the working voltage should be measured in accordance with sub-clause 2.10.4 and
7 B' t I/ G, C3 @: SAnnex M.3.1 to determine maximum peak, rms and/or dc values.2 Y" v# Q4 \& c a N
If the equipment is intended for connection to a U.S./Canadian Telecommunication Network and+ F1 h8 I$ t3 [8 ~$ K1 P
receives incoming analog telecommunication signals (e.g., from a Central Office), the following
/ n+ r! n, m m; }+ f4 ?2 kmaximum working voltages (TNV-3) should be assumed for purposes of determining required
: ^- e M6 k: N% Q# x* kclearances, creepage distances and electric strength test values:2 ]# B1 w! J; n) L1 ]# [# E0 [
a. peak: 200 V! @' e% J+ b9 B6 C# @. ~0 j
b. rms: 120 V
2 Y3 j9 W; G$ `- D. Wc. d.c.: 60 V5 ]: j+ k* C" K! ]% N" E/ B* N! M
176 PAG 60950-1 JULY 15, 2008
, p9 u* b1 I ]( d! X$ }5 s' w# VIf the equipment is intended for connection to a European Telecommunication Network, consult) {( V( \' q: M& h0 H
with IEC TR 62102, Technical Report on Electrical Safety Classification of interfaces for
9 t; \/ q' E! [; e3 E# mequipment to be connected to information and communications technology networks.
( s$ b+ m6 h: e7 C. g, W* `. lThe peak and rms values are used for clearance and electric strength determinations, and the1 \: Z* f3 I1 J; V( M
d.c. value is used for creepage distance.7 x0 x. Y6 L' A& O0 I
RATIONALE:# i \: S2 a# U* f S$ w1 D
Annex M (normative) describes maximum voltage levels associated with Telecommunication9 p; O0 Z) _- D& ~. h% K9 J& E
Signals that comply with FCC Part 68. The maximum peak value specified is 200 V referenced/ t/ s+ P- ~2 x- `
to earth. Since working voltages typically are measured to earth, this value should be considered. i" M4 x& v8 l9 A/ e! w
the maximum peak value in the U.S. and Canada.
' F2 E, i" M/ h3 @9 O0 RAlthough Annex M does not contain a corresponding rms value, 120 V rms is an approximation
" [- l" T: o! w. B9 Fof a composite 56.5 V dc and 300 Vp-p signal. Sub-clause 2.3.5 uses 120 V rms to simulate$ C+ O7 I# v& V: \( O" T
externally generated operating voltages. Therefore this value should be used for investigation to- o4 J- v( }$ Z4 h
this Standard. Also, sub-clause 2.10.4 indicates that cadenced ringing signals in TNV circuits
/ n r7 }" I. Mshall not be taken into account for determining creepage distances, thus a 60 Vd.c. value may0 z8 G; b8 @2 ^" [1 W( I w
be used.
% @# P$ h. ^/ J2 x6 y. }0 |* C" b根据class III equipment定义的条款4 y0 X5 h# y# Z: k! e/ {
1.2.4.3 CLASS III EQUIPMENT: equipment in which protection against electric shock relies upon, |( B/ \4 M0 m/ d" q! S
supply from SELV CIRCUITS and in which HAZARDOUS VOLTAGES are not generated
+ l$ e/ V; G2 I4 P$ Y) p0 j/ HNOTE For CLASS III EQUIPMENT, although there is no requirement for protection against electric shock, all other requirements of the standard apply.( k# V) n# k- h3 d6 T
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。
1 k6 v2 W3 u+ X/ x+ y& o& Y欢迎拍砖
7 K: e* _7 Z2 K; m2 G$ B0 {1 W
6 E0 X- n$ n& H' M: `7 G* B  [s:90] |
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