参考PAG clause 2.10.2-3 Working voltages in TNV circuits1 W t! X$ U# L$ ^8 ^
If the equipment generates a ringing signal and the circuit connects to a Telecommunication
6 A: x% [6 W( c( a2 KNetwork, the working voltage should be measured in accordance with sub-clause 2.10.4 and
( a3 r" T# Z$ e! VAnnex M.3.1 to determine maximum peak, rms and/or dc values.4 ?7 s3 }& [. }# C' u
If the equipment is intended for connection to a U.S./Canadian Telecommunication Network and5 f$ \8 v! |& N! O: I
receives incoming analog telecommunication signals (e.g., from a Central Office), the following
2 J* Q0 L. n5 l- G( ?1 j- emaximum working voltages (TNV-3) should be assumed for purposes of determining required; \% B& n1 A5 E5 Y1 n
clearances, creepage distances and electric strength test values:( g9 |! n6 D) D/ F* ]+ h0 E7 {
a. peak: 200 V
, b" Y; c5 B0 |b. rms: 120 V4 }$ J8 R$ w9 \) A: Q2 f
c. d.c.: 60 V! j. X5 Z9 g: J- f& [ ?
176 PAG 60950-1 JULY 15, 2008
1 }, K' [1 i+ SIf the equipment is intended for connection to a European Telecommunication Network, consult) v O1 P! G1 F' v
with IEC TR 62102, Technical Report on Electrical Safety Classification of interfaces for
+ a6 ?2 f5 K8 @3 \9 d; o6 hequipment to be connected to information and communications technology networks.
" W$ R1 b4 S' Y3 g- zThe peak and rms values are used for clearance and electric strength determinations, and the% W) t! U! m4 C9 l8 W3 \7 ~
d.c. value is used for creepage distance.
! l# M5 I4 G* j# f# {8 lRATIONALE:
1 _: v/ s' @) s( c0 ?+ H/ ~Annex M (normative) describes maximum voltage levels associated with Telecommunication, c% u" q/ ]( k6 i/ C3 c
Signals that comply with FCC Part 68. The maximum peak value specified is 200 V referenced
1 g/ O0 |# z) _# i. r: g- \to earth. Since working voltages typically are measured to earth, this value should be considered
" D; x% P/ Z) A j6 a* I% _5 D! mthe maximum peak value in the U.S. and Canada., Q6 ]4 Y0 _0 x( c- e
Although Annex M does not contain a corresponding rms value, 120 V rms is an approximation1 |' W) q b! e2 Q6 g
of a composite 56.5 V dc and 300 Vp-p signal. Sub-clause 2.3.5 uses 120 V rms to simulate
. ?1 ^. ]6 ?' r3 ^/ L& H; Z }1 `externally generated operating voltages. Therefore this value should be used for investigation to; _( ]: L" C O, J6 _
this Standard. Also, sub-clause 2.10.4 indicates that cadenced ringing signals in TNV circuits
2 |2 ?- L1 \) {1 ]shall not be taken into account for determining creepage distances, thus a 60 Vd.c. value may O% A3 H7 B" Z6 r
be used. |2 I4 v0 J4 Y- z+ u; y, Z
根据class III equipment定义的条款
2 _& k$ x+ h# C! u: s Z* q1.2.4.3 CLASS III EQUIPMENT: equipment in which protection against electric shock relies upon0 q$ D4 U; h" l+ W
supply from SELV CIRCUITS and in which HAZARDOUS VOLTAGES are not generated. r: k) l# i+ X8 C
NOTE For CLASS III EQUIPMENT, although there is no requirement for protection against electric shock, all other requirements of the standard apply.
5 q: f/ G6 y- f- y# v$ s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。
* G, I7 j [+ h( G) C欢迎拍砖
; z4 @) J3 O( }
W9 k1 A" F6 j  [s:90] |
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