参考PAG clause 2.10.2-3 Working voltages in TNV circuits
' H8 x( k3 H7 n9 n0 }If the equipment generates a ringing signal and the circuit connects to a Telecommunication2 K8 E2 B' D7 X) P! s! X
Network, the working voltage should be measured in accordance with sub-clause 2.10.4 and& @7 e# \. c0 L& F) }
Annex M.3.1 to determine maximum peak, rms and/or dc values.) ?: W: a8 O3 y, i6 X) u% t
If the equipment is intended for connection to a U.S./Canadian Telecommunication Network and0 s. z' Z. X% u+ h
receives incoming analog telecommunication signals (e.g., from a Central Office), the following
' ]& l$ @8 L5 Amaximum working voltages (TNV-3) should be assumed for purposes of determining required
3 c* \( w L8 u% d8 oclearances, creepage distances and electric strength test values:+ y% A/ ? y" }4 E/ [ q* R
a. peak: 200 V6 R! i0 A3 k+ W
b. rms: 120 V
( E6 }. t/ u) `c. d.c.: 60 V& [8 @+ Q3 g, i4 a( x" Z
176 PAG 60950-1 JULY 15, 2008
* y3 E* p9 F, d' _ V3 wIf the equipment is intended for connection to a European Telecommunication Network, consult
/ Y! @* r% e* Cwith IEC TR 62102, Technical Report on Electrical Safety Classification of interfaces for; q0 {. f. u. g( W
equipment to be connected to information and communications technology networks.
" P6 k, z3 Z. j v, j1 N- `) I, AThe peak and rms values are used for clearance and electric strength determinations, and the
: I) K5 z1 R- W6 Rd.c. value is used for creepage distance.
2 Z% I S" j3 ?2 f6 t5 xRATIONALE:$ k$ t2 H# B* n3 [0 d0 s
Annex M (normative) describes maximum voltage levels associated with Telecommunication
6 k* o' H( d7 }9 \' z1 ^Signals that comply with FCC Part 68. The maximum peak value specified is 200 V referenced
% ], {" }" Y5 Y) H; }: jto earth. Since working voltages typically are measured to earth, this value should be considered+ o' W( m2 A5 d& v- e7 [5 ]/ S$ R7 E
the maximum peak value in the U.S. and Canada.
: ^' N0 b- V$ ^/ sAlthough Annex M does not contain a corresponding rms value, 120 V rms is an approximation( i- h! m1 }: T' m' j+ ~
of a composite 56.5 V dc and 300 Vp-p signal. Sub-clause 2.3.5 uses 120 V rms to simulate8 n" \% z! K/ r, H
externally generated operating voltages. Therefore this value should be used for investigation to6 x3 q% Q* A5 \1 |
this Standard. Also, sub-clause 2.10.4 indicates that cadenced ringing signals in TNV circuits
, o6 `# d0 d) H, z% }shall not be taken into account for determining creepage distances, thus a 60 Vd.c. value may) r. }4 _9 k2 V
be used.* v3 O% }9 l6 g0 A! e/ l
根据class III equipment定义的条款( N. u4 o5 a6 i) p+ H2 o! G
1.2.4.3 CLASS III EQUIPMENT: equipment in which protection against electric shock relies upon
! S1 ]; N1 [) v! `9 Dsupply from SELV CIRCUITS and in which HAZARDOUS VOLTAGES are not generated
v/ s3 _5 t$ xNOTE For CLASS III EQUIPMENT, although there is no requirement for protection against electric shock, all other requirements of the standard apply.
9 x- X5 F4 u. o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。- |3 \8 _( R% \( ]8 N$ M# G1 a: Y# Z
欢迎拍砖
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