Last Editor Paul Cox - Siemens ST950 Handbook

Any third parties making alterations to such equipment / PELV installations must
consider the electrical requirements for PELV and the above in what they do, and
should only attempt such alterations if they are competent to do so.
The controller monitors its signal outputs for both positive and negative voltages with
respect to earth for its conflict system. In order to ensure the ELV voltage band is
maintained, positive voltages with respect to earth are clamped by the controller.
Should a positive voltage be applied to the signal outputs, the controller will consume
current to maintain a maximum positive voltage of approximately 0.8 volts at the
controller terminals.
Should a source with a large current sourcing capability be applied, catastrophic
damage may result. The extent and results of such damage cannot be predicted or
guaranteed.
Security classification Unrestricted
Version 4
Last Editor Paul Cox
Document Name ST950 General Handbook
Copyright © Siemens plc 2015. All Rights Reserved.
Mobility Division, Traffic Solutions
Sopers Lane, Poole, Dorset, BH17 7ER
Page 6 of 107
Status Issued
Date 16-Jul-2015
Document No. 667/HB/46000/000
Mobility is a division of Siemens Plc