12 Terms and abbreviations
OSSD
Output Signal Switch Device
PDDB
Proximity devices with defined
behaviour under fault condi-
tions
PFH
Probability of (dangerous)
(PFH
)
Failure per Hour
D
PL
Performance Level
SIL
Safety Integrity Level
SILCL
Safety Integrity Level
T
Mission time
M
PL to EN ISO 13849-1
SIL 1-4 to IEC 61508� The higher the
SIL, the lower the probability that a safety
function will fail�
According to IEC 62061
claim limit
Lifetime to IEC 60947-5-3
(= max� service life)
UK
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