Only BRK CO alarms with a "smart interconnect" can be interconnected
with smoke and heat alarms. The smart interconnect sends a unique
signal for smoke and CO alarms on one interconnect wire. With non-smart
interconnect CO products, no electrical hazard is associated with such
a connection of CO and smoke alarms. However, homeowner confusion can
arise when an alarm condition exists when these two devices are
interconnected as they have different horn patterns.