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Re: Continuous Current Capacity of Panels, Jacks, and Plugs


I have been looking at ITU-T I.430 (11/95). This is Basic Rate ISDN which
(of course) uses an RJ-45. It has some stuff in it for power.
("TE" is the network side device, "NT" is the terminal side device.)
They seem to be talking a nominal 40V, 200 mA. There are several power
situations and configurations. This is (I believe) a bussed device so
things such as power direction can get confusing. I suggest you get a copy
and look for yourself. The edited excerpts below are designed to whet your
interest and get you started.

Geoff Thompson
9.1.3 Power feeding voltage
Requirements for power feeding are given for a basic voltage range of 34 V
to 42 V from the power source. For some networks (for example, PBX), a
higher maximum voltage of 56.5 V is desirable to allow compatibility with
48 V power sources used for other purposes.

In the following detailed requirements for TEs and power sources (see
9.2.2, 9.2.3, 9.3.2, 9.3.3), the voltage limits given are for the basic
range, with the values for the optional increased voltage range in
(GOT: Notes to above paragraph deleted for brevity)

9.2.4 Short circuit protection
Power sources shall provide short-circuit protection. This requirement may
be checked by applying a short-circuit for a period of 30 minutes, after
which the power source shall be able to provide its rated PCUs (GOT note: A
PCU is for most purposes 100 mW) within 10 seconds (60 seconds in the case
of interface at the S-reference point). Verification of compliance may be
combined with the test described in 9.7.4.
42 Recommendation I.430 (11/95)

9.3.1 Power consumption unit
The power which a TE is designed to draw from power source 1 or 2 should be
given in terms of “power consumption units”. ....

A TE may be designed to draw any number of PCUs from power source 1 or 2,
up to a maximum of 80 NPCU for
normal mode. In restricted mode, the maximum that a TE may be designed to
draw is 4 RPCU for PS1, and 21 RPCU
for PS2.
(GOT: That's 8 watts by my calcs.)

9.2 Power available from NT
9.2.1 Power source 1 normal and restricted mode
... power source 1 together with any separate power source as described in
9.1, shall provide at least 10 power consumption units (normal) at a TE
interface. The power required to be available at the source will depend on
the interface cable configuration. [Power Consumption Units (PCU) are
defined in 9.3.1.]

9.4 PS1 current transient
The rate of change of current drawn by a TE from power source 1 shall not
exceed 5 mA/ms.

9.6 Galvanic isolation
TEs shall provide galvanic isolation between power source 1/2 and the
earths of additional sources of power and/or of other equipment. Isolation
shall be a minimum of 1 Mohm when measured at 500 V DC between an interface
conductor and any one of the following points: AC mains earth; all pins of
any external interfaces; or any conductive.surface. Equipment must also
comply with the applicable IEC safety specifications. (This provision is
intended to preclude earth loops or paths which could result in currents
that would interfere with the satisfactory operation of the TE. It is
independent of any requirement, for such isolation, related to safety which
may result from the study under way in IEC-ACOS/TES.)

At 04:53 PM 2/3/00 -0500, Kee, John H, JR (John) wrote:
>Hi Everyone:
>I have been following the Study Groups work on DTE Power via MDI and I have
>discussed some of the issues with attendees. Some feedback I received from
>the January meeting was that some connecting hardware (jacks, modular panels
>or otherwise) with printed circuit board technology have a maximum operating
>current of 250 milliamperes.
>One applicable standard for communications circuit accessories is the UL
>standard    UL1863. This standard specifies a Fault current test but does no
>specify a continuous operating current. The current-carrying parts are
>subjected to 2.2 amperes for 30 minutes and 7.0 amperes for 5 seconds.
> This is a request to anyone with information about the maximum operating
>current of communications circuit accessories such as the cross-connects,
>jacks, and plugs used to implement the EIA/TIA-568-B.1 type cabling systems.
>John H. Kee Jr.
| Geoffrey O. Thompson                    |
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