IFM Electronic AC015S Notice D'utilisation Originale page 23

For a classification to EN 954 category 4 or EN 61508 SIL3, positively
driven mechanical contacts to EN IEC 60947-5-1, rated for a voltage
> 120 V and a curr ent > 0.8 A, must be connected.
Wiring
A+: AS-i +
A-: AS-i -
S11-S12/
S21-S22: switching input
mechanical
contact S-I1 / S-I2
LEDs 1: switching status indication
inputs S-I1, S-I2
LEDs 2: AS-i, FAULT
X1-X2: external LED alarm output
6