参考PAG clause 2.10.2-3 Working voltages in TNV circuits# x. c* J5 f4 h3 u& x7 A
If the equipment generates a ringing signal and the circuit connects to a Telecommunication
+ k& b% B2 S1 Z4 Q) `$ aNetwork, the working voltage should be measured in accordance with sub-clause 2.10.4 and
6 [/ y) w0 _% oAnnex M.3.1 to determine maximum peak, rms and/or dc values.+ l% a' Z M' f# E6 T! W
If the equipment is intended for connection to a U.S./Canadian Telecommunication Network and' ^* @( s T- T% l
receives incoming analog telecommunication signals (e.g., from a Central Office), the following
# p' T7 {0 A9 b. F- ] X& }% k* Hmaximum working voltages (TNV-3) should be assumed for purposes of determining required
# P: j+ p7 ~8 U H8 _. Tclearances, creepage distances and electric strength test values:# }( v0 z4 h7 ^- C
a. peak: 200 V
$ S- t/ p; g! Y/ cb. rms: 120 V
( c5 o* N1 W6 O" @3 Yc. d.c.: 60 V& E% X8 l1 b8 @0 o4 [! T+ Q: _9 D
176 PAG 60950-1 JULY 15, 2008. y f- Q# R" d6 Y0 Z& N
If the equipment is intended for connection to a European Telecommunication Network, consult4 Q0 S. w" b) ^' Y l
with IEC TR 62102, Technical Report on Electrical Safety Classification of interfaces for
. k0 w& t. r* D- [. kequipment to be connected to information and communications technology networks.
9 l& ~/ h1 b: z- J! bThe peak and rms values are used for clearance and electric strength determinations, and the& C, G b4 Y% p8 w0 ?1 C3 O; Z
d.c. value is used for creepage distance.
# U; Y/ B3 D8 G! d3 {1 ?' w, ORATIONALE:
% ~5 |5 \8 ^9 W! B, h3 iAnnex M (normative) describes maximum voltage levels associated with Telecommunication: y4 S" O/ D7 f: Q
Signals that comply with FCC Part 68. The maximum peak value specified is 200 V referenced
4 N" G2 A( e. x( ?to earth. Since working voltages typically are measured to earth, this value should be considered2 K6 b+ n0 T+ W* B% M" \5 u' C* P
the maximum peak value in the U.S. and Canada.% W2 O+ @7 J: u* |' w& |
Although Annex M does not contain a corresponding rms value, 120 V rms is an approximation8 f' [ M+ l& D7 A; t l
of a composite 56.5 V dc and 300 Vp-p signal. Sub-clause 2.3.5 uses 120 V rms to simulate
1 Y1 Y3 _* ]0 j& M2 h. V Qexternally generated operating voltages. Therefore this value should be used for investigation to" j/ B/ F/ P+ B9 d' e* D
this Standard. Also, sub-clause 2.10.4 indicates that cadenced ringing signals in TNV circuits3 C8 |! i3 Q2 C. C& q9 w/ I
shall not be taken into account for determining creepage distances, thus a 60 Vd.c. value may/ b8 m: `3 ^' g
be used.6 X0 R0 Q& h! e& I: u1 }6 a* Q' l& b
根据class III equipment定义的条款! x1 T) C$ Q% {& s' h. n
1.2.4.3 CLASS III EQUIPMENT: equipment in which protection against electric shock relies upon$ w% n" W9 ?: d- m Q1 Y
supply from SELV CIRCUITS and in which HAZARDOUS VOLTAGES are not generated B8 x* ]6 g: h) V' u! F7 U
NOTE For CLASS III EQUIPMENT, although there is no requirement for protection against electric shock, all other requirements of the standard apply.' z3 k" B7 Y0 O) s L
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。
) x( [9 T& X: {- k2 x; k1 U% e( l9 y$ ?欢迎拍砖
' P2 J, J) o& B* u8 o' w
% e* e# ^, g5 ?4 X5 `+ }/ t  [s:90] |
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