参考PAG clause 2.10.2-3 Working voltages in TNV circuits5 G5 Z* v& Y$ L3 T" P5 J6 a1 e
If the equipment generates a ringing signal and the circuit connects to a Telecommunication- ?/ w- c. ?0 z- L2 E! x
Network, the working voltage should be measured in accordance with sub-clause 2.10.4 and
; C2 ]1 r' z1 o3 Q4 L2 A: `Annex M.3.1 to determine maximum peak, rms and/or dc values.
5 T& v. W3 `4 H) d% z5 r) J3 c* QIf the equipment is intended for connection to a U.S./Canadian Telecommunication Network and
7 h; E1 o G/ u; d$ n4 y- ereceives incoming analog telecommunication signals (e.g., from a Central Office), the following
8 B( O {8 C2 _, i% J8 i& g- R8 Omaximum working voltages (TNV-3) should be assumed for purposes of determining required) o2 Z; I% G3 C% b0 ^
clearances, creepage distances and electric strength test values:' x$ }7 f5 J' [
a. peak: 200 V
: i' B( q# r9 g+ bb. rms: 120 V) w s6 j& L O# j
c. d.c.: 60 V8 Q( U- ~2 b: m) p2 U+ p
176 PAG 60950-1 JULY 15, 2008, ]' K. D7 y1 k$ B% r7 X) c3 o b
If the equipment is intended for connection to a European Telecommunication Network, consult" |$ m3 R( I3 W) d6 D
with IEC TR 62102, Technical Report on Electrical Safety Classification of interfaces for. e7 L5 V) R& K* ?$ o( t$ s/ k
equipment to be connected to information and communications technology networks.
+ r3 ~ v" k) M. t6 L7 @5 QThe peak and rms values are used for clearance and electric strength determinations, and the
$ \$ a, W& z: ?! r4 ]# V5 Wd.c. value is used for creepage distance.' X/ B+ B& ?8 c' Y# G) W
RATIONALE: l3 {0 V9 s. i3 ]( U8 F+ D) b& z3 Z
Annex M (normative) describes maximum voltage levels associated with Telecommunication! R5 R# q0 c/ d
Signals that comply with FCC Part 68. The maximum peak value specified is 200 V referenced
; v7 ~6 y9 [# U d# jto earth. Since working voltages typically are measured to earth, this value should be considered
" u8 j/ e. B' `the maximum peak value in the U.S. and Canada.
/ _7 T6 X- O5 A3 v4 QAlthough Annex M does not contain a corresponding rms value, 120 V rms is an approximation- |$ P5 f: V$ ~4 G; }
of a composite 56.5 V dc and 300 Vp-p signal. Sub-clause 2.3.5 uses 120 V rms to simulate
) t4 Y/ T8 o& {4 y( `/ Sexternally generated operating voltages. Therefore this value should be used for investigation to
. c, q1 B' v$ Q. b) M6 q' }" ]this Standard. Also, sub-clause 2.10.4 indicates that cadenced ringing signals in TNV circuits
6 C6 a6 m3 N' ~2 q# T0 Kshall not be taken into account for determining creepage distances, thus a 60 Vd.c. value may+ b6 x; M, s+ h0 e ~
be used.& h$ S1 W- _1 P( x
根据class III equipment定义的条款
% h- x5 x, s& G. s! f1.2.4.3 CLASS III EQUIPMENT: equipment in which protection against electric shock relies upon
% Z7 O( D* |) M/ _9 ^9 |supply from SELV CIRCUITS and in which HAZARDOUS VOLTAGES are not generated
l+ s" o6 `' P9 e9 t) zNOTE For CLASS III EQUIPMENT, although there is no requirement for protection against electric shock, all other requirements of the standard apply.% Y: I5 K$ m7 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。$ v& J; G( K, z+ `& ]
欢迎拍砖
. l, V! ~. r+ t: v& E f5 [
, q# W8 o6 r3 o' }  [s:90] |
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发表于 2011-5-12 12:06
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