参考PAG clause 2.10.2-3 Working voltages in TNV circuits
# V: e5 M2 F. K& TIf the equipment generates a ringing signal and the circuit connects to a Telecommunication& e9 a9 O3 o$ y( H# u; j
Network, the working voltage should be measured in accordance with sub-clause 2.10.4 and( H+ p; } \2 q, r8 ~7 T% v
Annex M.3.1 to determine maximum peak, rms and/or dc values., J! N s4 w |0 M
If the equipment is intended for connection to a U.S./Canadian Telecommunication Network and
% i# J5 z4 l+ z7 V$ n. ireceives incoming analog telecommunication signals (e.g., from a Central Office), the following
9 q" {4 a9 K4 Hmaximum working voltages (TNV-3) should be assumed for purposes of determining required7 } F5 K* k/ }* E }8 ]
clearances, creepage distances and electric strength test values:
5 ]3 v7 A! X! `* ?. \! La. peak: 200 V
7 }' L3 {) O5 r, a* m: ?b. rms: 120 V
# j, D# L2 b" l( m3 v( @c. d.c.: 60 V
9 a. K! P3 T9 I2 u6 @176 PAG 60950-1 JULY 15, 2008
+ q3 c: W2 I2 }1 z! m5 CIf the equipment is intended for connection to a European Telecommunication Network, consult
; L3 X2 v+ ^; G5 E$ P% }with IEC TR 62102, Technical Report on Electrical Safety Classification of interfaces for
* H0 S7 L9 d8 c A9 U+ A9 Vequipment to be connected to information and communications technology networks.
/ T' B' O i8 j D QThe peak and rms values are used for clearance and electric strength determinations, and the H, o+ X# W/ p0 t
d.c. value is used for creepage distance.
# z4 o/ x3 v0 ZRATIONALE:
9 c( ^" H4 v4 pAnnex M (normative) describes maximum voltage levels associated with Telecommunication
: P& C- r" k- eSignals that comply with FCC Part 68. The maximum peak value specified is 200 V referenced
* [2 Y) w5 W! M0 L A) x) m! jto earth. Since working voltages typically are measured to earth, this value should be considered8 S8 x* A. D2 G: u( S1 g
the maximum peak value in the U.S. and Canada.6 Z6 x; m! r5 ]0 E# H" L+ j `+ ^ Z
Although Annex M does not contain a corresponding rms value, 120 V rms is an approximation
9 Z4 V. b! H" _8 gof a composite 56.5 V dc and 300 Vp-p signal. Sub-clause 2.3.5 uses 120 V rms to simulate7 b5 [4 |; e/ G' u
externally generated operating voltages. Therefore this value should be used for investigation to
6 t V: J* ^, J$ W% {% zthis Standard. Also, sub-clause 2.10.4 indicates that cadenced ringing signals in TNV circuits
, M. m( K4 r2 ?4 t; u mshall not be taken into account for determining creepage distances, thus a 60 Vd.c. value may* G% B- {+ ~5 [
be used.
_! p: p6 v) x* a8 `根据class III equipment定义的条款
3 S7 ^6 Z8 N# l7 k$ ^8 U1.2.4.3 CLASS III EQUIPMENT: equipment in which protection against electric shock relies upon1 L5 c+ h. D& r- W0 g, \& N
supply from SELV CIRCUITS and in which HAZARDOUS VOLTAGES are not generated, K. R7 w( n# Y1 r# z0 y' C
NOTE For CLASS III EQUIPMENT, although there is no requirement for protection against electric shock, all other requirements of the standard apply. q1 G1 r- a8 j+ s6 e! K, b
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。
: W7 o) K4 o# f$ q6 W0 V( U. B欢迎拍砖: q7 L4 j) X% U- e$ |) S) q8 ^
) l5 k- U1 Y8 |$ K
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