参考PAG clause 2.10.2-3 Working voltages in TNV circuits, n& e2 G$ N9 a9 q; a' m7 v2 A
If the equipment generates a ringing signal and the circuit connects to a Telecommunication
$ F* A. j: z/ Z. ~Network, the working voltage should be measured in accordance with sub-clause 2.10.4 and- U6 O% \/ t2 Z
Annex M.3.1 to determine maximum peak, rms and/or dc values.
0 t4 M+ q% V9 eIf the equipment is intended for connection to a U.S./Canadian Telecommunication Network and& m4 }& @' j: Y8 [; d* g: r9 ]
receives incoming analog telecommunication signals (e.g., from a Central Office), the following& I+ g, R$ z: e; A% _
maximum working voltages (TNV-3) should be assumed for purposes of determining required j! v" Z2 ~- C% [4 `# W
clearances, creepage distances and electric strength test values:9 E0 `8 r. \: h2 J2 g0 C+ w) K r$ w# j
a. peak: 200 V) `! O; e% T n) C
b. rms: 120 V8 f( L3 ]& f- [0 D
c. d.c.: 60 V# o. S3 E- Z. \& G& d6 e
176 PAG 60950-1 JULY 15, 2008
) R% N: f( N4 B8 NIf the equipment is intended for connection to a European Telecommunication Network, consult
1 E5 ~5 p. O6 x; \; qwith IEC TR 62102, Technical Report on Electrical Safety Classification of interfaces for
9 @8 I8 g. F3 e% T- c4 tequipment to be connected to information and communications technology networks.
- {0 c5 d4 r8 h9 e4 f( lThe peak and rms values are used for clearance and electric strength determinations, and the8 g2 M% L! R# @( g
d.c. value is used for creepage distance.
" f+ k& ^- Y! _: iRATIONALE:9 A- G2 x3 T( \. l
Annex M (normative) describes maximum voltage levels associated with Telecommunication, |; T0 a2 E1 M& C: g
Signals that comply with FCC Part 68. The maximum peak value specified is 200 V referenced/ {! B; e" K1 F
to earth. Since working voltages typically are measured to earth, this value should be considered# C6 f4 ` f x) A2 d
the maximum peak value in the U.S. and Canada.
1 H G5 J6 o1 y* {; h3 h$ IAlthough Annex M does not contain a corresponding rms value, 120 V rms is an approximation
/ l( Q4 r1 Q3 s" H1 N) e4 ~of a composite 56.5 V dc and 300 Vp-p signal. Sub-clause 2.3.5 uses 120 V rms to simulate
' L7 f, r/ \; ~" ]externally generated operating voltages. Therefore this value should be used for investigation to& M- K: s7 q, J; W% ~- A7 _
this Standard. Also, sub-clause 2.10.4 indicates that cadenced ringing signals in TNV circuits6 }, {# v+ I+ P. {. I% ?: U+ H
shall not be taken into account for determining creepage distances, thus a 60 Vd.c. value may
+ l" D/ s8 \, t/ Wbe used.: \, Z- A$ R) q0 B9 z
根据class III equipment定义的条款, [3 i! r7 P: @
1.2.4.3 CLASS III EQUIPMENT: equipment in which protection against electric shock relies upon5 y, w! ]% C- S; i& B# D
supply from SELV CIRCUITS and in which HAZARDOUS VOLTAGES are not generated
& s# h4 q& `' ]7 K8 F9 INOTE For CLASS III EQUIPMENT, although there is no requirement for protection against electric shock, all other requirements of the standard apply.# R" A% ^/ B2 j8 N6 R
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。
: l8 Z2 j) u7 S: a- F& u欢迎拍砖4 E% O, t2 t& E' i& f
$ q c& v! @; p" |' B0 a
 [s:90] |
/2 
|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