Siemens SIMATIC PCS 7 OSx - Role_Change Command

Alarm Applications/Failover Option
A-7
SIMATIC PCS 7 OSx 4.0.0 Hardware (PA RISC)
In the normal non-alarm condition, a 24 V AC or 24 VDC supplies power to
Channel #1 and Channel #2 common, 2L.
When Output Channel #1 experiences a warning alarm condition, the
normally-open contact closes, supplying power to Relay #1. Energizing this
relay closes the normally-open contact, causing Annunciator #1 to sound.
When Output Channel #2 experiences a critical alarm condition, the
normally-open contact closes, supplying power to Relay #2. Energizing this
relay closes the normally-open contact, causing Annunciator #2 to sound.
Power
Supply
Alarm Board
Output
Channel
#2
Output
Channel
#1
24 V AC or 24 VDC
120 V AC
Annunciator
#1
Annunciator
#2
Power
Supply
Relay #1
Relay #2
Q0.5
2L
Q0.4
Q0.3
2L
Figure A-2 Dual Alar ms
Theory