参考PAG clause 2.10.2-3 Working voltages in TNV circuits
) {! _5 C$ r; y3 q# AIf the equipment generates a ringing signal and the circuit connects to a Telecommunication1 Q ~4 P; j0 L) W
Network, the working voltage should be measured in accordance with sub-clause 2.10.4 and* D6 i2 z5 O/ `
Annex M.3.1 to determine maximum peak, rms and/or dc values.' Y) ~& O1 J* j6 c
If the equipment is intended for connection to a U.S./Canadian Telecommunication Network and% @# x0 n6 e" R6 ]
receives incoming analog telecommunication signals (e.g., from a Central Office), the following2 O0 Y+ ~1 i& s0 H6 {- y
maximum working voltages (TNV-3) should be assumed for purposes of determining required; {/ o, U# }5 p% v2 _# @8 K
clearances, creepage distances and electric strength test values:% Y+ w- A. p& A% K$ y- x( D4 X" ~
a. peak: 200 V
; f$ L# @3 P2 z; S0 d( Pb. rms: 120 V% {# o9 B; ~0 w. p% P( x$ w) k: S) O
c. d.c.: 60 V
% g6 F9 ?, I: ?% w: O176 PAG 60950-1 JULY 15, 20087 A8 F, I7 Z4 m, c
If the equipment is intended for connection to a European Telecommunication Network, consult
6 f% ?: U) ]& xwith IEC TR 62102, Technical Report on Electrical Safety Classification of interfaces for
- O: @; K% q/ N# tequipment to be connected to information and communications technology networks.
4 Q" u9 d% e5 | iThe peak and rms values are used for clearance and electric strength determinations, and the4 C# K/ P5 \, I5 ]$ d8 g1 \% ~
d.c. value is used for creepage distance.# u) D% v ?) u
RATIONALE:
$ f& Q& x/ ?% \" v5 qAnnex M (normative) describes maximum voltage levels associated with Telecommunication, O$ a( h) Z: T' I7 W
Signals that comply with FCC Part 68. The maximum peak value specified is 200 V referenced
- @ v6 m: q% F" x9 oto earth. Since working voltages typically are measured to earth, this value should be considered
* J( x0 s$ o0 S6 d$ A% Jthe maximum peak value in the U.S. and Canada.
( n) x! s- f2 Q/ I3 ^3 Q [Although Annex M does not contain a corresponding rms value, 120 V rms is an approximation% Q e x0 h' A4 Z b7 f
of a composite 56.5 V dc and 300 Vp-p signal. Sub-clause 2.3.5 uses 120 V rms to simulate
- Y7 {( y- _' e% r) ?! Yexternally generated operating voltages. Therefore this value should be used for investigation to
, K, }; d/ A$ J0 S4 ~ Zthis Standard. Also, sub-clause 2.10.4 indicates that cadenced ringing signals in TNV circuits- o, Y0 Y/ i8 b9 r$ h
shall not be taken into account for determining creepage distances, thus a 60 Vd.c. value may7 Y5 ?% B0 V$ z, W! E2 Q3 `/ ?
be used. D, d. V3 f6 p) N# D( g
根据class III equipment定义的条款
: L. U# c% q2 W) N1 p1.2.4.3 CLASS III EQUIPMENT: equipment in which protection against electric shock relies upon! K) a9 h* N3 K- H0 `0 m' i
supply from SELV CIRCUITS and in which HAZARDOUS VOLTAGES are not generated
' a0 p/ w S" {2 PNOTE For CLASS III EQUIPMENT, although there is no requirement for protection against electric shock, all other requirements of the standard apply.
( @. v/ N8 z% \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 X$ T# }; z4 ~7 Y7 V8 h$ T欢迎拍砖
& A! ~( b: @! ^, {( Y( i5 z1 x* I! N3 t
 [s:90] |
/1 
|关于安规|小黑屋|安规QQ群|Archiver|手机版|安规网
( 粤ICP13023453-10 )
窥视卡
雷达卡
发表于 2011-5-12 12:06
显身卡
楼主