Harman BSS Soundweb London BLU-100 Guide D'installation page 12

6
OPTO Output
In addition to the six standard LOGIC OUTPUTS, there is an isolated output, which fails
safe (open circuit) if the unit becomes faulty.
47kOhm
log
potentiometer
unconnected
ladder
switch
2 wire mode
+supply
voltage
relay
ground
10K-100kOhm
linear
potentiometer
ladder
switch
3 wire mode
LED
relay