参考PAG clause 2.10.2-3 Working voltages in TNV circuits
. S$ {& C: l4 zIf the equipment generates a ringing signal and the circuit connects to a Telecommunication' X6 a7 \* W6 H: d" U
Network, the working voltage should be measured in accordance with sub-clause 2.10.4 and
$ U% ?. [5 j- `" O; Y6 i6 ~4 e$ fAnnex M.3.1 to determine maximum peak, rms and/or dc values.
) j7 q4 I% W s; {8 mIf the equipment is intended for connection to a U.S./Canadian Telecommunication Network and1 x9 T; I O5 K1 z. p$ _/ k
receives incoming analog telecommunication signals (e.g., from a Central Office), the following. M% c }+ ~1 a. B; s
maximum working voltages (TNV-3) should be assumed for purposes of determining required
" D( e: |+ j( dclearances, creepage distances and electric strength test values:
/ U; J3 V% Z! A }8 ua. peak: 200 V- T/ {2 B- l K
b. rms: 120 V
8 I- S( \2 Z5 Ic. d.c.: 60 V
! c% Q! [( D& F6 d! e' w% Q, U* `3 h176 PAG 60950-1 JULY 15, 2008
% I$ [; n* }, B ^* mIf the equipment is intended for connection to a European Telecommunication Network, consult
/ o5 v! ?) r9 Q' e: rwith IEC TR 62102, Technical Report on Electrical Safety Classification of interfaces for5 s) F, _1 V5 r1 D
equipment to be connected to information and communications technology networks.
+ D. m7 y1 ?7 R' Y1 a' B1 }7 i9 f$ pThe peak and rms values are used for clearance and electric strength determinations, and the
3 H$ w3 ]- `. y0 G$ @- f+ Od.c. value is used for creepage distance.
# \4 ?/ M X6 P; z5 p, [: W/ _RATIONALE:" V E f7 i0 W& Z) g2 V
Annex M (normative) describes maximum voltage levels associated with Telecommunication4 \) Y# J2 |! F6 x* I
Signals that comply with FCC Part 68. The maximum peak value specified is 200 V referenced
8 `+ M/ n5 R, _ i3 @# b' Oto earth. Since working voltages typically are measured to earth, this value should be considered! {" o+ r$ X6 M. T. W. N
the maximum peak value in the U.S. and Canada.
e, g$ Q- n7 h) Z# jAlthough Annex M does not contain a corresponding rms value, 120 V rms is an approximation( x( z- i3 }9 x
of a composite 56.5 V dc and 300 Vp-p signal. Sub-clause 2.3.5 uses 120 V rms to simulate
0 y. C) d$ `; ~3 |. Qexternally generated operating voltages. Therefore this value should be used for investigation to
/ O, w- t0 n2 O' Mthis Standard. Also, sub-clause 2.10.4 indicates that cadenced ringing signals in TNV circuits: V3 b1 W( h4 q
shall not be taken into account for determining creepage distances, thus a 60 Vd.c. value may
8 {8 p% d( ]# v# |be used.
2 a% L! D2 e. L E+ T( M% r2 h8 V根据class III equipment定义的条款
5 k; Y3 L/ P% f9 B5 f* d) L+ @1 C1.2.4.3 CLASS III EQUIPMENT: equipment in which protection against electric shock relies upon3 e& y5 e, c" `. R+ w+ r
supply from SELV CIRCUITS and in which HAZARDOUS VOLTAGES are not generated( n9 N5 t) W- [ `
NOTE For CLASS III EQUIPMENT, although there is no requirement for protection against electric shock, all other requirements of the standard apply.
: j( R7 }) y# S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。
/ B" X3 W* j: Y* ?4 m& o% ^7 d欢迎拍砖4 R9 b0 R3 t( n0 X( i( l
: a5 [# k7 j; C/ T* ^4 g
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