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European Safety Systems Ltd.
Impress House, Mansell Road, Acton, London W3 7QH [email protected] Tel: +44 (0)208 743 8880
www.e2s.com Fax: +44 (0)208 740 4200
Document No. D191-00-601-IS Issue 1 20-03-2020 Sheet 12 of 8
Note: - Cable fault
Between the panel and the first unit, a cable short, increases the current (presenting a short circuit to the panel), and a cable
cut/open reduces current (presenting an open circuit to the panel).
In series topology a cable short between units will short out one of the current sense resistors which results in an increase in
the current used by the unit, and a cable cut/open reduces current (presenting an open circuit to the panel).
In star topology a cable short between units will short circuit the SIL 2 monitoring line hence presenting a short circuit to the
panel, an open circuit fault on one of the units will effectively remove one of the current sense resistors reducing total effective
resistance hence decreasing the total current seen by the panel.
