20
13 Terms and abbreviations
OSSD
Output Signal Switch Device
PDDB
Proximity devices with defined
behaviour under fault condi-
tions
PFH
(PFH
D
)
Probability of (dangerous)
Failure per Hour
PL
Performance Level
PL to EN ISO 13849-1
SIL
Safety Integrity Level
SIL 1-4 to IEC 61508� The higher the
SIL, the lower the probability that a safety
function will fail�
SIL
cl
Safety Integrity Level
claim limit
According to IEC 62061
T
M
Mission time
Lifetime to EN 60947-5-3
(= max� service life)