参考PAG clause 2.10.2-3 Working voltages in TNV circuits
& n P; \* p$ z0 OIf the equipment generates a ringing signal and the circuit connects to a Telecommunication
: C. j: u6 e$ i5 }2 DNetwork, the working voltage should be measured in accordance with sub-clause 2.10.4 and. U9 q" a; t$ }7 i/ q
Annex M.3.1 to determine maximum peak, rms and/or dc values.
/ E# e: ? E2 E9 ~8 x2 M' h% JIf the equipment is intended for connection to a U.S./Canadian Telecommunication Network and5 [+ ~( W; l7 P; p+ O3 |
receives incoming analog telecommunication signals (e.g., from a Central Office), the following
/ t, o2 L4 t ^ f5 X8 m( i0 Ymaximum working voltages (TNV-3) should be assumed for purposes of determining required7 y/ m- w- x" c# d" F6 a7 S9 K
clearances, creepage distances and electric strength test values:+ q! q5 ^% q7 c$ y
a. peak: 200 V
5 h9 j/ a; r* \b. rms: 120 V
. y8 j7 z( o- Qc. d.c.: 60 V
0 j$ f+ Z2 n9 z" V) T176 PAG 60950-1 JULY 15, 2008
2 N! q5 @' k5 F* A* CIf the equipment is intended for connection to a European Telecommunication Network, consult. K/ Y+ p! \" i3 h3 j6 h$ Y1 ]% Z
with IEC TR 62102, Technical Report on Electrical Safety Classification of interfaces for# ~. t' ~. J5 u% x$ F S
equipment to be connected to information and communications technology networks.. A- _ \2 v+ C* X* U3 a- }
The peak and rms values are used for clearance and electric strength determinations, and the
- e% a" ~( F7 c- b9 Fd.c. value is used for creepage distance.
# c% \6 u Q' Q0 ERATIONALE:
. X* e" v4 |* YAnnex M (normative) describes maximum voltage levels associated with Telecommunication& v3 R" e0 o# f
Signals that comply with FCC Part 68. The maximum peak value specified is 200 V referenced7 z# R; B% }4 e' d/ {0 g% H2 v
to earth. Since working voltages typically are measured to earth, this value should be considered
0 n2 ~1 C7 j0 X5 z( T' K' L) othe maximum peak value in the U.S. and Canada.
7 Y5 h* K9 `$ s8 p% j% \. `% PAlthough Annex M does not contain a corresponding rms value, 120 V rms is an approximation, N; n! Z7 |, H! C/ {
of a composite 56.5 V dc and 300 Vp-p signal. Sub-clause 2.3.5 uses 120 V rms to simulate' Z2 z9 ~7 k) p! \
externally generated operating voltages. Therefore this value should be used for investigation to
. q% M" B0 T8 X5 V7 ~( O) Pthis Standard. Also, sub-clause 2.10.4 indicates that cadenced ringing signals in TNV circuits
) x* A* `7 _4 t5 p6 mshall not be taken into account for determining creepage distances, thus a 60 Vd.c. value may" R9 k2 k; z! t8 Y0 P8 _
be used.
" _9 T% C$ T; T" K3 W+ p3 O根据class III equipment定义的条款
7 T7 C6 z. ^, X" X& ^1.2.4.3 CLASS III EQUIPMENT: equipment in which protection against electric shock relies upon
9 O! {0 g9 G/ O; i7 ksupply from SELV CIRCUITS and in which HAZARDOUS VOLTAGES are not generated+ P0 E2 r6 y% r# N
NOTE For CLASS III EQUIPMENT, although there is no requirement for protection against electric shock, all other requirements of the standard apply.9 N1 }( }1 e+ K. }+ H# E8 t7 h* j
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。/ r2 Z5 P( c, J5 p) w2 |0 ]9 P
欢迎拍砖
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发表于 2011-5-12 12:06
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