参考PAG clause 2.10.2-3 Working voltages in TNV circuits& m$ B/ B1 b9 X$ U C' t& {
If the equipment generates a ringing signal and the circuit connects to a Telecommunication M2 T( x" m F# Z
Network, the working voltage should be measured in accordance with sub-clause 2.10.4 and/ r) V4 y+ K0 C8 c' M" m ?
Annex M.3.1 to determine maximum peak, rms and/or dc values.
/ @; S v! \: mIf the equipment is intended for connection to a U.S./Canadian Telecommunication Network and, Z% E' t9 x1 F! @+ Q( q
receives incoming analog telecommunication signals (e.g., from a Central Office), the following
/ Z5 [, Q$ o, Smaximum working voltages (TNV-3) should be assumed for purposes of determining required& U( |% J T ?2 E! [
clearances, creepage distances and electric strength test values:% u; x2 q& w# u$ {# b( o3 t) b* K+ a
a. peak: 200 V
( {; ~" c( ]; V( tb. rms: 120 V
1 c! E5 z/ u& L5 e. K! v1 ^+ Cc. d.c.: 60 V& V% u( N _ L
176 PAG 60950-1 JULY 15, 2008& g* A- p Y. o) p
If the equipment is intended for connection to a European Telecommunication Network, consult1 X- S( k) i3 X' k
with IEC TR 62102, Technical Report on Electrical Safety Classification of interfaces for
% a4 I0 b ?, }8 l$ Pequipment to be connected to information and communications technology networks.1 _6 t1 w# a! s8 K. T2 e1 h
The peak and rms values are used for clearance and electric strength determinations, and the; w( T* y& g, r0 L. m9 P
d.c. value is used for creepage distance.+ h+ f2 ^8 R& y8 B4 V5 F5 S
RATIONALE:
2 h, ^8 r% |9 n: l+ h8 I$ l" p; lAnnex M (normative) describes maximum voltage levels associated with Telecommunication& s0 E9 M L" U% H }3 L$ w8 Z
Signals that comply with FCC Part 68. The maximum peak value specified is 200 V referenced6 q9 u6 p3 _0 X' W
to earth. Since working voltages typically are measured to earth, this value should be considered
! A( P! s& M, _/ }the maximum peak value in the U.S. and Canada." h4 r* M! i( C3 q
Although Annex M does not contain a corresponding rms value, 120 V rms is an approximation
* y( f+ A4 Q$ d B; M9 e. _of a composite 56.5 V dc and 300 Vp-p signal. Sub-clause 2.3.5 uses 120 V rms to simulate
$ x( e; x6 m% K1 ^externally generated operating voltages. Therefore this value should be used for investigation to
- r- J! Z* H! l" |; V5 hthis Standard. Also, sub-clause 2.10.4 indicates that cadenced ringing signals in TNV circuits) X2 B, t( N0 I
shall not be taken into account for determining creepage distances, thus a 60 Vd.c. value may4 ]) z. h9 L5 A
be used.4 T! C9 @ ]8 M4 d$ c
根据class III equipment定义的条款, X% f8 {6 g& Q3 \: T, X
1.2.4.3 CLASS III EQUIPMENT: equipment in which protection against electric shock relies upon$ d8 T" L" [( L) u# F# x7 B* o/ F
supply from SELV CIRCUITS and in which HAZARDOUS VOLTAGES are not generated
: |) w* @$ F, b) q- P6 M7 yNOTE For CLASS III EQUIPMENT, although there is no requirement for protection against electric shock, all other requirements of the standard apply.
1 n- C- l! }$ I/ H$ 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。/ U$ N/ n8 A4 j/ ^* Y1 Q8 P) c/ u, i0 x
欢迎拍砖
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