Dear Zhang, As fair as I know, there are many old twisted pair wirings around the world without standardized cross-sectional are. Therefore they checked it and set maximum limit from central office to 1.3A. However on the subscriber side you will never get more than few 10mA (usually 20-40mA). This is enough for analogue telephone to operate. Therefore you will never exceed 15W on subscriber side.
To summarize, limit of 1.3A is applicable for CO equipment, and limit 15VA for subscriber units (analogue or ISDN phones, modems etc). Please consider this is not applicable for Power over Ethernet. This is local network and not for public telecommunication network. Best regards, Bostjan On 14. sep. 2013, at 02:57, "Zhangguoqing (A)" <zhangguoq...@huawei.com> wrote: > Dear Peter, > > Thank you for your reply. > > If a transmit equipment can deliver 1.3A current into telecommunication > network, then in the corresponding receive equipment (terminals), 1.3A > current is available, do you think so? > > My question is why the standard states the transmit equipment can deliver > 1.3A (max.), but at the same time it states the power available from a > TELECOMMUNICATION NETWORK is limited to 15 VA? > > Zhang guoqing > > -----邮件原件----- > 发件人: Peter Tarver [mailto:ptar...@enphaseenergy.com] > 发送时间: 2013年9月14日 7:27 > 收件人: EMC-PSTC@LISTSERV.IEEE.ORG > 主题: Re: [PSES] question on clause 6.3 and 1.4.11 of IEC60950-1 > >> -----Original Message----- >> From: Zhangguoqing (A) [mailto:zhangguoq...@huawei.com] >> Sent: Wednesday, September 11, 2013 05:39 >> >> My question is , if a equipment intends to provide >> power over the telecommunication wiring system, the >> current and the power should be controlled at the same >> time? or, only the current should be controlled? > > > Zhang Guoqing - > > §1.4.11 is the assumed power available *from* a telecommunications network > to connected equipment (terminals). A POTS device, for example, with no > other power sources can be considered to be supplied by a 15 VA power > limited source. This plays nicely with the 15 VA limits you'll find in > the fire enclosure and internal wiring requirements. > > §6.3 relates to current generated by equipment and *delivered into* a > telecommunications network under worst-case loading conditions. The > intent is to protect wiring and wiring devices typical in > telecommunications networks, in particular modular plugs/jacks, line cords > and the like. > > > Regards, > > Peter Tarver > > > This email message is for the sole use of the intended recipient(s) and may > contain confidential and/or privileged information. If you are not an > intended recipient, you may not review, use, copy, disclose or distribute > this message. 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