参考PAG clause 2.10.2-3 Working voltages in TNV circuits
6 S# t Y$ {1 L& X' WIf the equipment generates a ringing signal and the circuit connects to a Telecommunication
, @' F5 H/ F2 E INetwork, the working voltage should be measured in accordance with sub-clause 2.10.4 and& X* S; I# O1 e0 j- Q. v
Annex M.3.1 to determine maximum peak, rms and/or dc values.6 a' R" g# C* g: i* o2 \
If the equipment is intended for connection to a U.S./Canadian Telecommunication Network and c5 D- W7 C7 I& [2 e) j3 c1 m8 W
receives incoming analog telecommunication signals (e.g., from a Central Office), the following, ~1 r5 A) N/ z6 r1 w% L
maximum working voltages (TNV-3) should be assumed for purposes of determining required {! G( @+ a% {5 W% ?
clearances, creepage distances and electric strength test values:
9 K# [- q& u7 q. ta. peak: 200 V% S" C8 G7 B( U' ~" |/ C, f# O
b. rms: 120 V( k' x; U' L0 ^8 [/ |
c. d.c.: 60 V
6 w6 G7 Q3 ~ G176 PAG 60950-1 JULY 15, 2008
4 ?0 F! z1 S; A2 K2 h# t4 \If the equipment is intended for connection to a European Telecommunication Network, consult
, A5 y5 ?' E$ B' {with IEC TR 62102, Technical Report on Electrical Safety Classification of interfaces for9 |9 v- z! }6 [" K$ r, r, ~- h
equipment to be connected to information and communications technology networks.
h2 |, A1 n& l( c+ Y; M( tThe peak and rms values are used for clearance and electric strength determinations, and the. R: `3 @( w, o7 g1 x! j
d.c. value is used for creepage distance.9 [1 J V! f* I
RATIONALE:- v( K' S$ t' u' H4 L! J+ x
Annex M (normative) describes maximum voltage levels associated with Telecommunication" f" L6 g5 ]2 |; ], x( A, Z( Z. P
Signals that comply with FCC Part 68. The maximum peak value specified is 200 V referenced [) O5 T: s7 Z1 r
to earth. Since working voltages typically are measured to earth, this value should be considered6 L* y% N" K2 _# W. s1 f
the maximum peak value in the U.S. and Canada.
. P' k4 k/ o3 T4 t. ^Although Annex M does not contain a corresponding rms value, 120 V rms is an approximation; s L5 @# j! M5 v! F
of a composite 56.5 V dc and 300 Vp-p signal. Sub-clause 2.3.5 uses 120 V rms to simulate, n6 w2 Y% T+ j2 n: V
externally generated operating voltages. Therefore this value should be used for investigation to
( O' a8 P+ V# l- ^8 ?$ V6 Z: v) fthis Standard. Also, sub-clause 2.10.4 indicates that cadenced ringing signals in TNV circuits
, U4 G' j9 F5 rshall not be taken into account for determining creepage distances, thus a 60 Vd.c. value may& e! I2 l7 ^8 i1 J
be used.; p- e7 w: w# M, H
根据class III equipment定义的条款
( y: d" x- ^5 V+ u6 h, }7 e1.2.4.3 CLASS III EQUIPMENT: equipment in which protection against electric shock relies upon
: ]% S: a# P- e+ |9 d$ n. ^supply from SELV CIRCUITS and in which HAZARDOUS VOLTAGES are not generated+ @! }$ N$ N8 g+ W* B' w$ L
NOTE For CLASS III EQUIPMENT, although there is no requirement for protection against electric shock, all other requirements of the standard apply.
; Z, g9 u* `9 g7 M* p6 C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。
. J+ J! ^: ]" K; ?0 T+ N: O欢迎拍砖
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