Handheld Terminal
Connection
User's Manual, Version: 1.3
27
© KEBA 2007
The safety category 3 means, that one failure must not lead to the loss of
the safety function, and whenever possible, the single failure is detected.
The chapters „Example of Connection with PILZ PST1 Control Relay“ and
“Example of Connection with ELAN SRB-NA-R-C.27/S1 Control Relay”
show how the
safety category 3
can be fulfilled with the KeTop and its
safety-related parts. The entire concept of the machine must be laid out ac-
cording to the principles of safety category 3.
The monitoring of the simultaneity by the control relay is necessary, be-
cause otherwise maybe a failure culmination would not be recognised and
this would cause the loss of safeness:
Example: If one circuit of the enabling device switches to the enabled state
as a result of a failure and after some time the second circuit also switches
to the enabled state as a result of an failure, then no de-energisation by the
enabling device would be possible.
Further the EN 60204-1:1997 prescribes that the enabling switches shall be
connected to a category 0 stop or a category 1 stop, that means the energy
must be switched off.