参考PAG clause 2.10.2-3 Working voltages in TNV circuits; l4 j3 x, R, N
If the equipment generates a ringing signal and the circuit connects to a Telecommunication! N7 L- `, M! s1 z: ?: @* c/ [
Network, the working voltage should be measured in accordance with sub-clause 2.10.4 and3 E& d: U( d2 h8 g0 s4 q e) c
Annex M.3.1 to determine maximum peak, rms and/or dc values.
# i( J. @7 I2 [2 d7 Q5 }If the equipment is intended for connection to a U.S./Canadian Telecommunication Network and
1 z J' C6 f: [8 U5 a9 E/ kreceives incoming analog telecommunication signals (e.g., from a Central Office), the following0 j) J, P( q; s u0 H+ G8 j
maximum working voltages (TNV-3) should be assumed for purposes of determining required$ L% o% g# {, [2 u; c0 o
clearances, creepage distances and electric strength test values:
6 z' Z) A" U5 e' B6 }5 `a. peak: 200 V
5 \% d' H' Q2 Ob. rms: 120 V3 ]2 r8 h$ n4 s5 O4 o3 e0 I. Q
c. d.c.: 60 V1 L9 t3 n" x: Y ?! C* R8 C
176 PAG 60950-1 JULY 15, 2008
% K! L* |- | F& Q3 V+ zIf the equipment is intended for connection to a European Telecommunication Network, consult
# g' E2 G" T( W& J. @' Awith IEC TR 62102, Technical Report on Electrical Safety Classification of interfaces for Y( \8 r- j [! X0 g% o* h9 _
equipment to be connected to information and communications technology networks." w" g. O F1 n( X3 D' w, c
The peak and rms values are used for clearance and electric strength determinations, and the; Y x( ?3 U. n. L9 _8 [
d.c. value is used for creepage distance.
' F& a0 q+ K9 ~* x/ P/ ]9 yRATIONALE:
" j# e; @- o5 W: }4 r4 q0 uAnnex M (normative) describes maximum voltage levels associated with Telecommunication
- q% F4 P- x+ V g* \( W, U, \Signals that comply with FCC Part 68. The maximum peak value specified is 200 V referenced
# C' I# X2 p) ^8 c* {6 zto earth. Since working voltages typically are measured to earth, this value should be considered. w+ Z* M, ]0 @/ j" O; Y" u& x
the maximum peak value in the U.S. and Canada.
. N1 U% [9 v& b$ \0 ^, E0 R* rAlthough Annex M does not contain a corresponding rms value, 120 V rms is an approximation: S! H5 V" y; X( M4 B$ a: ]
of a composite 56.5 V dc and 300 Vp-p signal. Sub-clause 2.3.5 uses 120 V rms to simulate
8 P9 M# W+ M6 R- V% r" Yexternally generated operating voltages. Therefore this value should be used for investigation to o% D, L: N7 X- A) G
this Standard. Also, sub-clause 2.10.4 indicates that cadenced ringing signals in TNV circuits: j6 o2 {5 v3 I9 a& H# d
shall not be taken into account for determining creepage distances, thus a 60 Vd.c. value may+ ^' o7 b$ P5 F" I9 G. X; v
be used.
$ a/ q/ U3 a: K2 J根据class III equipment定义的条款0 Z& A. L u9 ?: s0 N5 Q- @# r2 ?
1.2.4.3 CLASS III EQUIPMENT: equipment in which protection against electric shock relies upon& E# R5 A F* ?9 t- W
supply from SELV CIRCUITS and in which HAZARDOUS VOLTAGES are not generated( J7 E! M" H+ [
NOTE For CLASS III EQUIPMENT, although there is no requirement for protection against electric shock, all other requirements of the standard apply.
; P3 c; \6 K, L$ f. N" F) u4 M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。
, i4 ], Y5 }9 d欢迎拍砖. E1 p: l# i8 _' _/ y% `1 t
& |) Y3 O! g: }$ q$ U  [s:90] |
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