参考PAG clause 2.10.2-3 Working voltages in TNV circuits
F& r( H" r, W0 YIf the equipment generates a ringing signal and the circuit connects to a Telecommunication
/ @6 C& S- g* l" p; y( I+ X- }Network, the working voltage should be measured in accordance with sub-clause 2.10.4 and
; q- Z$ R. B* l& O. l/ F1 KAnnex M.3.1 to determine maximum peak, rms and/or dc values.9 I8 A% b/ _ U `7 P
If the equipment is intended for connection to a U.S./Canadian Telecommunication Network and
1 `3 ~9 @' g/ s+ y) b* F0 K6 [9 v# Vreceives incoming analog telecommunication signals (e.g., from a Central Office), the following
6 f5 }8 {0 }# t# ~$ N$ Hmaximum working voltages (TNV-3) should be assumed for purposes of determining required6 ]# R8 O Z f1 H h) O6 ^) B
clearances, creepage distances and electric strength test values:
; l$ A7 b+ G! I5 y& f% da. peak: 200 V8 u+ n5 v8 ~' k) O1 \# _% A5 r+ i
b. rms: 120 V/ ~1 ^/ w2 i6 J9 t' I. I
c. d.c.: 60 V
' U1 f% [3 c0 |) D' e/ ~176 PAG 60950-1 JULY 15, 20088 x* r3 Q. Q: o( g( C* t
If the equipment is intended for connection to a European Telecommunication Network, consult
k0 @0 Q3 U+ v4 ~$ r% mwith IEC TR 62102, Technical Report on Electrical Safety Classification of interfaces for
6 D) d, I) A# e6 i3 I% e, pequipment to be connected to information and communications technology networks.
2 @% u% @' f( c! f4 hThe peak and rms values are used for clearance and electric strength determinations, and the
; ]# p' `- w2 u5 pd.c. value is used for creepage distance.% b2 h% n) i0 C2 b2 x+ V
RATIONALE:
& x- p. O& v; A$ Q; D3 zAnnex M (normative) describes maximum voltage levels associated with Telecommunication
, h+ j0 V0 C1 r* I- ]" gSignals that comply with FCC Part 68. The maximum peak value specified is 200 V referenced
0 g' g m) S9 a4 F; g7 x6 bto earth. Since working voltages typically are measured to earth, this value should be considered/ A* ]5 ]8 y1 z
the maximum peak value in the U.S. and Canada.( k0 R7 P- }" [* e; X
Although Annex M does not contain a corresponding rms value, 120 V rms is an approximation8 d3 @! E$ W |6 X0 d: d9 i* i
of a composite 56.5 V dc and 300 Vp-p signal. Sub-clause 2.3.5 uses 120 V rms to simulate1 z1 c! G7 ]4 z
externally generated operating voltages. Therefore this value should be used for investigation to2 b0 i, s% A0 U, t B' x
this Standard. Also, sub-clause 2.10.4 indicates that cadenced ringing signals in TNV circuits% w( \) A( q) V; t, Y
shall not be taken into account for determining creepage distances, thus a 60 Vd.c. value may s5 D6 R& g% x1 ~ E' _0 g! i
be used.6 ?7 w" l, }2 E8 `+ A9 w% [* P
根据class III equipment定义的条款( O* P2 ~' H/ d* }7 H0 B- Y2 T# n
1.2.4.3 CLASS III EQUIPMENT: equipment in which protection against electric shock relies upon V9 v j; U2 Y ?
supply from SELV CIRCUITS and in which HAZARDOUS VOLTAGES are not generated) Q2 w. T6 Y% u- H( Z- A* q
NOTE For CLASS III EQUIPMENT, although there is no requirement for protection against electric shock, all other requirements of the standard apply.! m/ d) T! t( S1 S. V( S. q1 X
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。& i* w4 X. A, v# X
欢迎拍砖
" p& i( ]! @ K9 l
1 j* d) i9 J' m3 v. f  [s:90] |
|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