参考PAG clause 2.10.2-3 Working voltages in TNV circuits
! k6 M) A ~6 I. |8 U3 _If the equipment generates a ringing signal and the circuit connects to a Telecommunication- O" \8 N8 O, x$ G9 s& c: T$ S
Network, the working voltage should be measured in accordance with sub-clause 2.10.4 and% J2 p+ @" }& D, l0 `
Annex M.3.1 to determine maximum peak, rms and/or dc values.
0 {# h" N! B4 V5 S. k. D# {If the equipment is intended for connection to a U.S./Canadian Telecommunication Network and5 E" t; u( z% p2 {$ S
receives incoming analog telecommunication signals (e.g., from a Central Office), the following& _) x' a4 T2 K/ M4 r
maximum working voltages (TNV-3) should be assumed for purposes of determining required
G1 H2 S; W4 \# j/ bclearances, creepage distances and electric strength test values:
9 a3 M' N+ t# r$ k! T# Ca. peak: 200 V( g8 _/ u$ m E9 ^0 k5 [# P$ N9 L, Y
b. rms: 120 V1 o ~# v3 T: |8 S: Q2 v4 u2 S" V
c. d.c.: 60 V6 P. Z/ _: m. p: Y( G' H- G
176 PAG 60950-1 JULY 15, 2008
) U; H. e- @2 p8 w- _# Y2 ^If the equipment is intended for connection to a European Telecommunication Network, consult+ s- Z; k( K. R
with IEC TR 62102, Technical Report on Electrical Safety Classification of interfaces for9 b U" U+ `; D$ g, P* E
equipment to be connected to information and communications technology networks.( S8 F1 Y7 {( ^; n" f7 [
The peak and rms values are used for clearance and electric strength determinations, and the; ?+ c$ m! d- q# N% c- B M
d.c. value is used for creepage distance.
' B# a4 w) e2 t& p' sRATIONALE:
5 }4 D% n7 T! O0 v( T! z7 zAnnex M (normative) describes maximum voltage levels associated with Telecommunication
" W- D6 V9 m% `% f4 d3 hSignals that comply with FCC Part 68. The maximum peak value specified is 200 V referenced/ j( u- n% Y# S" r/ k0 v+ ?
to earth. Since working voltages typically are measured to earth, this value should be considered. |9 x# }* I3 n5 h2 c( Y9 f
the maximum peak value in the U.S. and Canada.
- e" s' ?* i* E% f2 L$ SAlthough Annex M does not contain a corresponding rms value, 120 V rms is an approximation
# q, v2 X5 r; e' F! ^1 J, dof a composite 56.5 V dc and 300 Vp-p signal. Sub-clause 2.3.5 uses 120 V rms to simulate
: A/ H y7 `/ n1 }) H) l, zexternally generated operating voltages. Therefore this value should be used for investigation to* U3 q5 f# R' v1 i% O' t1 T
this Standard. Also, sub-clause 2.10.4 indicates that cadenced ringing signals in TNV circuits
3 D. @9 X8 [# V3 y, t& nshall not be taken into account for determining creepage distances, thus a 60 Vd.c. value may- ^# H& B& x1 D) \7 e
be used.: X. I9 p+ y% |0 @
根据class III equipment定义的条款
' K0 ]7 z& j( c( }# F, X1.2.4.3 CLASS III EQUIPMENT: equipment in which protection against electric shock relies upon
# C- y+ G0 m7 Ssupply from SELV CIRCUITS and in which HAZARDOUS VOLTAGES are not generated
* o6 ?. P9 F) Q; F+ e' g9 X& t" ]NOTE For CLASS III EQUIPMENT, although there is no requirement for protection against electric shock, all other requirements of the standard apply.
6 \. S7 ^4 J4 e% 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。6 y" F7 ? N3 U d3 U# E6 Z
欢迎拍砖4 n! G( |! {) J5 ~
: Z4 p3 W7 A, b+ n4 i% T0 @
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