参考PAG clause 2.10.2-3 Working voltages in TNV circuits
4 S5 b$ M" j" Z/ O, B% e, t" T2 UIf the equipment generates a ringing signal and the circuit connects to a Telecommunication
9 v. _+ a" n; U- D6 }Network, the working voltage should be measured in accordance with sub-clause 2.10.4 and
+ G( U) h5 o/ T' V- K D; SAnnex M.3.1 to determine maximum peak, rms and/or dc values.. Y9 A* I+ l9 O* U! H/ o @
If the equipment is intended for connection to a U.S./Canadian Telecommunication Network and5 r/ P6 Q; [* L8 [
receives incoming analog telecommunication signals (e.g., from a Central Office), the following$ h8 P% Z2 e) a
maximum working voltages (TNV-3) should be assumed for purposes of determining required
9 v" o% B" P5 Uclearances, creepage distances and electric strength test values:5 d6 e! F; v2 Q' s: H- Y
a. peak: 200 V
) a- v" c2 G) hb. rms: 120 V
% D4 n- M; R" ^ r) s5 v! Fc. d.c.: 60 V
) e8 Z3 g* ~0 S( U# v# r; v {176 PAG 60950-1 JULY 15, 2008: I1 R- l! \) ]1 c5 A8 L
If the equipment is intended for connection to a European Telecommunication Network, consult
; l* J. Q9 Z' H5 E n6 owith IEC TR 62102, Technical Report on Electrical Safety Classification of interfaces for; l* w6 m; E. R D9 v3 }6 N' U6 @# y
equipment to be connected to information and communications technology networks.
9 T( ~. _/ U+ {5 Y( ~9 _The peak and rms values are used for clearance and electric strength determinations, and the3 k' I. U$ G) Q" J/ \; ]- ]
d.c. value is used for creepage distance." Z1 g! M) d+ V! @2 l
RATIONALE:" X# W: n1 f, C; Z* n$ {$ ]
Annex M (normative) describes maximum voltage levels associated with Telecommunication
- Z+ {$ t& S$ P' Q6 ], }7 _8 KSignals that comply with FCC Part 68. The maximum peak value specified is 200 V referenced
K4 l7 U+ v0 e ^. qto earth. Since working voltages typically are measured to earth, this value should be considered; {6 b4 s0 F; r
the maximum peak value in the U.S. and Canada.
+ t( K: o: Z- }; \6 N4 T6 jAlthough Annex M does not contain a corresponding rms value, 120 V rms is an approximation
, d! t Y2 d9 i" hof a composite 56.5 V dc and 300 Vp-p signal. Sub-clause 2.3.5 uses 120 V rms to simulate
" W0 E$ ?, q( A2 @2 N! e+ Nexternally generated operating voltages. Therefore this value should be used for investigation to
* r% f1 \6 P; jthis Standard. Also, sub-clause 2.10.4 indicates that cadenced ringing signals in TNV circuits
$ h; @ v( y% L1 D6 xshall not be taken into account for determining creepage distances, thus a 60 Vd.c. value may
/ @2 P$ ]) c9 R" b) u- X2 Bbe used.1 { s: w$ k1 I7 Y$ b
根据class III equipment定义的条款
& i& j! h' {* j6 L4 B- o5 f8 V1.2.4.3 CLASS III EQUIPMENT: equipment in which protection against electric shock relies upon
% t( E$ y" g& V& q! rsupply from SELV CIRCUITS and in which HAZARDOUS VOLTAGES are not generated$ h V8 i, f% s8 Q0 {
NOTE For CLASS III EQUIPMENT, although there is no requirement for protection against electric shock, all other requirements of the standard apply.6 P: ^7 @4 [' a- j* E
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。
* g2 Z% w" ]& I: {欢迎拍砖5 ]9 i% ^# S& x8 P6 K: f8 Y
* V9 V. l R$ E/ D5 q
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发表于 2011-5-12 12:06
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