_______________________________________________________________________________
From: DouglasScott on Fri, Aug 15, 1997 8:30 AM
Subject: RE: User warnings on RS232 connections (IEC950)
To: cwel...@grtpa01.grt.ch.etn.com
Chris,
We do not take any special actions re: interface connectors on our products. We
put in the user manual a pix (drawing) of the connectors and describe what they
are for. In our case, either proprietary RS-422, SCSI or remote control. We
define what the pins are for each connector. We do say that shielded cables are
required and we usually provide either the RS-422 or SCSI cables. We do not
provide the remote control cable. Where we bring the supplies directly to the
connector (5v, 12v) we fuse these to stay within our requirements for '950.
We do not do any warning labels and have not given much thought to telling
people not to connect unsafe stuff to our products. I guess that has always
been assumed and implied. Not in 14 years have I ever had a safety agency raise
the question you did about telling others what not to connect or that it should
maintain '950 requirements. Interesting point.
________________________
Regards,
Scott Douglas
Principal Compliance Engineer
ECRM Incorporated
Telephone: 1-508-851-0207
Facsimilie: 1-508-851-7016
e-mail: sdoug...@ecrm.com
________________________
_______________________________________________________________________________
From: cwel...@grtpa01.grt.ch.etn.com on Thu, Aug 14, 1997 4:57 PM
Subject: User warnings on RS232 connections (IEC950)
To: emc-p...@majordomo.ieee.org
I am struggling with some requirements relative to interconnecting
equipment and EN60950.
My question is generic but I thought the example of an RS232 comport on a
PC would highlight my questions as to - "what is reasonable or required for
warnings to the user relative to connection to other equipment".
Background
EN60950 has the following sections:
Section 2.10.1 states - "Where equipment is intended to be electrically
connected to other equipment interconnection circuits shall be selected to
provide continued conformance with the requirements of 2.3 for SELV
circuits, and with the requirements of clause 6 for TNV circuits, after
making connections between equipment."
Section 1.7.2 Safety Instructions - "If it is necessary to take special
precautions to avoid the introduction of hazards when operation, installing,
maintaining , transporting or storing equipment , the manufacturer shall
have available the necessary instructions."
Safety relationships of an RS232 port (as I understand them)
1) The RS232 port is a SELV circuit as an extension of the 12 or 5 Volt
secondary of the PC power supply.
2) The RS232 port is referenced to protective earth through the PC power
cord.
3) The RS232 port is not typically galvanically isolated.
4) The RS232 port could be connected to a product that is not IEC950
qualified.
Questions:
1) Are any warning symbols required at this port such as a yellow triangle
with an exclamation mark inside?
2) Is there any requirement to warn the user not to connect to any other
equipment that would violate the SELV nature of this circuit?
3) When I have reviewed CE marked PCs there does not appear to be much
addressing this example or any related example. It appears that they are
relying on :
3a) Requirement that local safety codes be followed
3b) Clear definition of the port.
Is this adequate?
Summary
I am struggling with the conflicts of "due diligence" in following the
standards and not wanting to appear overly restrictive relative to our
competitors. If you have any guidance in this or related examples I would
very much like to here your war stories.
Regards
Chris Wells
Sr Des Eng.
Cutler-Hammer
Pittsburgh, Pa, USA
ph 1 (412) 494-3723
wellscd @ch.etn.com
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Subject: User warnings on RS232 connections (IEC950)
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